diff --git a/210902/BOJ_1325.cpp b/210902/BOJ_1325.cpp
new file mode 100644
index 0000000..69902db
--- /dev/null
+++ b/210902/BOJ_1325.cpp
@@ -0,0 +1,68 @@
+#include<bits/stdc++.h>
+#define xx first
+#define yy second
+using namespace std;
+using ll = long long;
+using pii = pair<int,int>;
+using pll = pair<ll,ll>;
+using tpi = tuple<int,int,int>;
+using tpl = tuple<ll,ll,ll>;
+using dpi = pair<pii,pii>;
+using dpl = pair<pll,pll>;
+using pis = pair<int,string>;
+using psi = pair<string,int>;
+
+const int INF = 0x3f3f3f3f;
+const ll INF64 = 0x3f3f3f3f3f3f3f3f;
+
+int N,M;
+vector<int> adj[10001]{};
+bool vi[10001]{};
+vector<pii> arr;
+
+int bfs(int st){
+    memset(vi,0,sizeof(vi));
+    queue<int> q;
+    q.push(st);
+    vi[st] = true;
+
+    int ret = 1;
+    while (!q.empty()) {
+        int cn = q.front();
+        q.pop();
+
+        for(auto next : adj[cn]){
+            if(vi[next]) continue;
+            q.push(next);
+            vi[next] = true;
+            ret++;
+        }
+    }
+    return ret;
+}
+
+int main() {
+    ios_base::sync_with_stdio(0);
+    cin.tie(0);
+    cin>>N>>M;
+    int a,b;
+    for(int i=0; i<M; i++){
+        cin>>a>>b;
+        adj[b].push_back(a);
+    }
+
+    for(int i=1; i<=N; i++) arr.push_back({bfs(i), i});
+
+    sort(arr.begin(), arr.end(), [&](pii a, pii b) -> bool{
+        if(a.xx == b.xx) return a.yy < b.yy;
+        return a.xx > b.xx;
+    });
+
+    int pre = -1;
+    for(auto val : arr){
+        if(pre!=-1 && pre!=val.xx) break;
+        pre = val.xx;
+        cout<<val.yy<<'\n';
+    }
+
+}
\ No newline at end of file
diff --git a/210902/BOJ_18405.java b/210902/BOJ_18405.java
new file mode 100644
index 0000000..8b74969
--- /dev/null
+++ b/210902/BOJ_18405.java
@@ -0,0 +1,90 @@
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Queue;
+import java.util.StringTokenizer;
+
+public class Main{
+    static int N, K, S, X, Y;
+    static int[][] m;
+    static boolean[][] vi;
+    static ArrayList<ArrayList<Tiii>> adj; // 바이러스 1~K 의 위치 저장
+    static int dy[] = {-1,1,0,0};
+    static int dx[] = {0,0,-1,1};
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); // 입력
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); // 출력
+        StringTokenizer st = new StringTokenizer(br.readLine());;
+
+        N = Integer.parseInt(st.nextToken());
+        K = Integer.parseInt(st.nextToken());
+
+        m = new int[N][N];
+        vi = new boolean[N][N];
+        adj = new ArrayList<>();
+        for(int i=0; i<=K; i++) adj.add(new ArrayList<>());
+        for(int i=0; i<N; i++){
+            st = new StringTokenizer(br.readLine());
+            for(int j=0; j<N; j++){
+                m[i][j] = Integer.parseInt(st.nextToken());
+                // m[i][j]번 바이러스들의 위치를 adj.get(m[i][j])에 인접리스트 형태로 저장
+                if(m[i][j] != 0) adj.get(m[i][j]).add(new Tiii(i,j,0)); // Tiii(y,x,d) : y축좌표, x축좌표, 현재 지난 시간(초)
+            }
+        }
+        st = new StringTokenizer(br.readLine());
+        S = Integer.parseInt(st.nextToken());
+        X = Integer.parseInt(st.nextToken());
+        Y = Integer.parseInt(st.nextToken());
+
+        bfs();
+
+        bw.write(m[X-1][Y-1]+""); // 정답 bufferWriter에 저장
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    static void bfs(){
+        Queue<Tiii> q = new ArrayDeque<>();
+        for(int i=1; i<=K; i++){
+            for (Tiii next : adj.get(i)) { // 1번 바이러스들 부터 큐에 순차적으로 저장
+                q.add(next);
+                vi[next.y][next.x] = true; // 방문처리
+            }
+        }
+
+        while(!q.isEmpty()){
+            Tiii poll = q.poll();
+            int cy = poll.y;
+            int cx = poll.x;
+            int cd = poll.d;
+
+            if(cd == S) continue; // S초일때 답을 구해야 하므로 S초라면 증식 중지
+
+            for(int i=0; i<4; i++){
+                int ny = cy + dy[i];
+                int nx = cx + dx[i];
+                if(ny<0 || nx<0 || ny>=N || nx>=N || vi[ny][nx] || m[ny][nx]!=0) continue;
+                q.add(new Tiii(ny,nx,cd+1)); // 증식할 수 있으면, 다음 y축과 x좌표 그리고 현재 지난시간(초)를 큐에 저장
+                vi[ny][nx] = true;
+                m[ny][nx] = m[cy][cx]; // 다음 위치에 바이러스 번호 업데이트
+            }
+        }
+    }
+
+    static class Tiii{ // y축, x축, 지난 시간(초)
+        int y,x,d;
+
+        public Tiii(int y, int x, int d) {
+            this.y = y;
+            this.x = x;
+            this.d = d;
+        }
+    }
+
+}
diff --git a/210902/BOJ_6188.java b/210902/BOJ_6188.java
new file mode 100644
index 0000000..f3a1fec
--- /dev/null
+++ b/210902/BOJ_6188.java
@@ -0,0 +1,84 @@
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Queue;
+import java.util.StringTokenizer;
+
+public class Main{
+    static int N, M;
+    static ArrayList<ArrayList<Integer>> adj;
+    static int[] vi;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); // 입력
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); // 출력
+        StringTokenizer st = new StringTokenizer(br.readLine());;
+
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+
+        vi = new int[N+1];
+        Arrays.fill(vi, -1);
+        adj = new ArrayList<>();
+        for(int i=0; i<=N; i++) adj.add(new ArrayList<>());
+
+        int a,b;
+        for(int i=0; i<M; i++){
+            st = new StringTokenizer(br.readLine());;
+            a = Integer.parseInt(st.nextToken());
+            b = Integer.parseInt(st.nextToken());
+            adj.get(a).add(b);
+            adj.get(b).add(a);
+        }
+
+        int resNum = -1;
+        int resDist = bfs();
+        int resCnt = 0;
+        for(int i=1; i<=N; i++){
+            if(vi[i]!=resDist) continue;
+            if(resNum==-1) resNum = i;
+            resCnt++;
+        }
+
+        bw.write(resNum + " " + resDist + " " + resCnt);
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    static int bfs(){
+        Queue<Pii> q = new ArrayDeque<>();
+        q.add(new Pii(1,0));
+        vi[1] = 0;
+
+        int dist = 0;
+        while (!q.isEmpty()) {
+            Pii poll = q.poll();
+            int cn = poll.n;
+            int cd = poll.d;
+            dist = Math.max(dist, cd);
+
+            for (Integer next : adj.get(cn)) {
+                if(vi[next]>=0) continue;
+                q.add(new Pii(next, cd+1));
+                vi[next] = cd+1;
+            }
+        }
+        return dist;
+    }
+
+    static class Pii{
+        int n,d;
+
+        public Pii(int n, int d) {
+            this.n = n;
+            this.d = d;
+        }
+    }
+
+}
diff --git a/210902/BOJ_7576.java b/210902/BOJ_7576.java
new file mode 100644
index 0000000..45d8010
--- /dev/null
+++ b/210902/BOJ_7576.java
@@ -0,0 +1,84 @@
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.util.ArrayDeque;
+import java.util.Queue;
+import java.util.StringTokenizer;
+
+public class Main{
+    static int N, M;
+    static int[][] m;
+    static boolean[][] vi;
+    static int dy[] = {-1,1,0,0};
+    static int dx[] = {0,0,-1,1};
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); // 입력
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); // 출력
+        StringTokenizer st = new StringTokenizer(br.readLine());;
+
+        M = Integer.parseInt(st.nextToken());
+        N = Integer.parseInt(st.nextToken());
+
+        Queue<Tiii> q = new ArrayDeque<>();
+        m = new int[N][M];
+        vi = new boolean[N][M];
+        for(int i=0; i<N; i++){
+            st = new StringTokenizer(br.readLine());;
+            for(int j=0; j<M; j++){
+                m[i][j] = Integer.parseInt(st.nextToken());
+                if(m[i][j]==1) { // 익은 토마토 큐에 삽입
+                    q.add(new Tiii(0, i, j));
+                    vi[i][j] = true;
+                }
+            }
+        }
+
+        int ans = 0;
+        while (!q.isEmpty()) { // bfs
+            Tiii poll = q.poll();
+            int cd = poll.d;
+            int cy = poll.y;
+            int cx = poll.x;
+
+            ans = Math.max(ans, cd);
+
+            for(int i=0; i<4; i++){
+                int ny = cy + dy[i];
+                int nx = cx + dx[i];
+                if(ny<0 || nx<0 || ny>=N || nx>=M || vi[ny][nx] || m[ny][nx]==-1) continue;
+                q.add(new Tiii(cd + 1, ny, nx));
+                vi[ny][nx] = true;
+            }
+        }
+
+        int res = ans;
+        for(int i=0; i<N; i++){ // 익지않은 토마토 검사
+            for(int j=0; j<M; j++){
+                if(m[i][j]==-1) continue;
+                if(!vi[i][j]) {
+                    System.out.println(-1);
+                    System.exit(0);
+                }
+            }
+        }
+
+        bw.write(res+"");
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    static class Tiii{ // 시간, y좌표, x좌표
+        int d,y,x;
+
+        public Tiii(int d, int y, int x) {
+            this.d = d;
+            this.y = y;
+            this.x = x;
+        }
+    }
+
+}