diff --git "a/BOJ/1000-5000\353\262\210/JM_2151.java" "b/BOJ/1000-5000\353\262\210/JM_2151.java"
new file mode 100644
index 00000000..54d0423a
--- /dev/null
+++ "b/BOJ/1000-5000\353\262\210/JM_2151.java"
@@ -0,0 +1,84 @@
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.PriorityQueue;
+import java.util.StringTokenizer;
+
+public class JM_2151 {
+	static class Point implements Comparable<Point> {
+		int y, x;
+		int dir;
+		int dist;
+
+		public Point(int y, int x, int dir, int dist) {
+			this.y = y;
+			this.x = x;
+			this.dir = dir;
+			this.dist = dist;
+		}
+
+		@Override
+		public int compareTo(Point o) {
+			return this.dist - o.dist;
+		}
+	}
+	static int N;
+	static char[][] map;
+	static Point start;
+	static Point end;
+	static final int[][] DIR = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};
+
+	private static boolean inRange(int y, int x) {
+		return  0 <= y && y < N && 0 <= x && x < N;
+	}
+
+	private static int solve() {
+		PriorityQueue<Point> pq = new PriorityQueue<>();
+		boolean[][][] visited = new boolean[N][N][4];
+
+		for (int i = 0; i < 4; i++) {
+			pq.add(new Point(start.y, start.x, i, 0));
+		}
+
+		while (!pq.isEmpty()) {
+			Point curr = pq.poll();
+
+			visited[curr.y][curr.x][curr.dir] = true;
+
+			if(curr.y == end.y && curr.x == end.x) return curr.dist;
+
+			int ny = curr.y + DIR[curr.dir][0];
+			int nx = curr.x + DIR[curr.dir][1];
+
+			if(!inRange(ny, nx) || map[ny][nx] == '*' || visited[ny][nx][curr.dir]) continue;
+
+			if(map[ny][nx] == '!') {
+				pq.add(new Point(ny, nx, (curr.dir + 1) % 4, curr.dist + 1));
+				pq.add(new Point(ny, nx, (curr.dir + 3) % 4, curr.dist + 1));
+			}
+			pq.add(new Point(ny, nx, curr.dir, curr.dist));
+
+		}
+
+		return -1;
+	}
+
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		StringTokenizer st = new StringTokenizer(br.readLine());
+		N = Integer.parseInt(st.nextToken());
+
+		map = new char[N][N];
+		for (int i = 0; i < N; i++) {
+			map[i] = br.readLine().toCharArray();
+			for (int j = 0; j < N; j++) {
+				if(map[i][j] == '#') {
+					if(start == null) start = new Point(i, j, -1, 0);
+					else end = new Point(i, j, -1, 0);
+				}
+			}
+		}
+
+		System.out.println(solve());
+	}
+}
diff --git "a/BOJ/1000-5000\353\262\210/JM_3151.java" "b/BOJ/1000-5000\353\262\210/JM_3151.java"
new file mode 100644
index 00000000..c808705d
--- /dev/null
+++ "b/BOJ/1000-5000\353\262\210/JM_3151.java"
@@ -0,0 +1,65 @@
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.Arrays;
+import java.util.StringTokenizer;
+
+public class JM_3151 {
+	static int N;
+	static int[] A;
+
+	private static int lowerBound(int startIndex, int target) {
+		int lo = startIndex, hi = N - 1;
+		int ans = N;
+		while (lo <= hi){
+			int mid = (lo + hi) / 2;
+			if(target <= A[mid]) {
+				ans = mid;
+				hi = mid - 1;
+			}
+			else lo = mid + 1;
+		}
+		return ans;
+	}
+
+	private static int upperBound(int startIndex, int target) {
+		int lo = startIndex, hi = N - 1;
+		int ans = N;
+		while (lo <= hi){
+			int mid = (lo + hi) / 2;
+			if(target < A[mid]) {
+				ans = mid;
+				hi = mid - 1;
+			}
+			else lo = mid + 1;
+		}
+		return ans;
+	}
+
+	private static long solve() {
+		Arrays.sort(A);
+		long count = 0;
+		for (int i = 0; i < N; i++) {
+			for (int j = i + 1; j < N; j++) {
+				int target = 0 - (A[i] + A[j]);
+				int lowerIndex = lowerBound(j + 1, target);
+				int upperIndex = upperBound(j + 1, target);
+				count += upperIndex - lowerIndex;
+			}
+		}
+		return count;
+	}
+
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		StringTokenizer st = new StringTokenizer(br.readLine());
+		N = Integer.parseInt(st.nextToken());
+
+		A = new int[N];
+		st = new StringTokenizer(br.readLine());
+		for(int i = 0; i < N; i++) {
+			A[i] = Integer.parseInt(st.nextToken());
+		}
+		System.out.println(solve());
+	}
+}
diff --git "a/CodeTree/2023-2024\353\205\204/JM_\354\275\224\353\223\234\355\212\270\353\246\254_\353\251\224\354\213\240\354\240\200" "b/CodeTree/2023-2024\353\205\204/JM_\354\275\224\353\223\234\355\212\270\353\246\254_\353\251\224\354\213\240\354\240\200"
new file mode 100644
index 00000000..d6e952b3
--- /dev/null
+++ "b/CodeTree/2023-2024\353\205\204/JM_\354\275\224\353\223\234\355\212\270\353\246\254_\353\251\224\354\213\240\354\240\200"
@@ -0,0 +1,176 @@
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.Arrays;
+import java.util.StringTokenizer;
+
+public class JM_코드트리_메신저 {
+	static class Room {
+		int c;
+		boolean alert;
+		int authority;
+
+		int parent;
+		int leftChild;
+		int rightChild;
+
+		int[] effect;
+
+		public Room(int c) {
+			this.c = c;
+			this.alert = true;
+			this.parent = -1;
+			this.leftChild = -1;
+			this.rightChild = -1;
+			this.effect = new int[DEPTH + 1];
+		}
+
+		public void toggleAlert() {
+			this.alert = !this.alert;
+		}
+	}
+	static int N;
+	static int Q;
+	static Room[] rooms;
+	static final int DEPTH = 20;
+
+	private static void update(int c) {
+		while (c != 0) {
+			Room curr = rooms[c];
+			Arrays.fill(curr.effect, 0);
+			for (int i = 0; i <= curr.authority; i++) {
+				rooms[c].effect[i]++;
+			}
+
+			if(curr.leftChild != -1 && rooms[curr.leftChild].alert) {
+				for (int i = 1; i <= DEPTH; i++) {
+					curr.effect[i - 1] += rooms[curr.leftChild].effect[i];
+				}
+			}
+
+			if(curr.rightChild != -1 && rooms[curr.rightChild].alert) {
+				for (int i = 1; i <= DEPTH; i++) {
+					curr.effect[i - 1] += rooms[curr.rightChild].effect[i];
+				}
+			}
+
+			c = rooms[c].parent;
+		}
+	}
+
+	private static void swapParent(int c1, int c2) {
+		int p1 = rooms[c1].parent;
+		int p2 = rooms[c2].parent;
+
+		if(rooms[p1].leftChild == c1) {
+			rooms[p1].leftChild = c2;
+		} else if(rooms[p1].rightChild == c1) {
+			rooms[p1].rightChild = c2;
+		}
+
+		if(rooms[p2].leftChild == c2) {
+			rooms[p2].leftChild = c1;
+		} else if(rooms[p2].rightChild == c2) {
+			rooms[p2].rightChild = c1;
+		}
+
+		rooms[c1].parent = p2;
+		rooms[c2].parent = p1;
+
+		update(c1);
+		update(c2);
+	}
+
+	private static void changeAuthority(int c, int power) {
+		rooms[c].authority = power > DEPTH ? DEPTH : power;
+		update(c);
+	}
+
+	private static void toggleNotification(int c) {
+		rooms[c].toggleAlert();
+		update(c);
+	}
+
+	private static void initEffect(int c) {
+		if(c == -1) return;
+
+		Room curr = rooms[c];
+		for (int i = 0; i <= curr.authority; i++) {
+			rooms[c].effect[i]++;
+		}
+
+		initEffect(curr.leftChild);
+		initEffect(curr.rightChild);
+
+		if(curr.leftChild != -1) {
+			for (int i = 1; i <= DEPTH; i++) {
+				curr.effect[i - 1] += rooms[curr.leftChild].effect[i];
+			}
+		}
+
+		if(curr.rightChild != -1) {
+			for (int i = 1; i <= DEPTH; i++) {
+				curr.effect[i - 1] += rooms[curr.rightChild].effect[i];
+			}
+		}
+	}
+
+	private static void init(StringTokenizer st) {
+		rooms = new Room[N + 1];
+		for (int i = 0; i <= N; i++) {
+			rooms[i] = new Room(i);
+		}
+
+		for (int i = 1; i <= N; i++) {
+			int pIdx = Integer.parseInt(st.nextToken());
+			rooms[i].parent = pIdx;
+			if(rooms[pIdx].leftChild == -1) rooms[pIdx].leftChild = i;
+			else rooms[pIdx].rightChild = i;
+		}
+
+		for (int i = 1; i <= N; i++) {
+			rooms[i].authority = Integer.parseInt(st.nextToken());
+			if(rooms[i].authority > DEPTH) rooms[i].authority = DEPTH;
+		}
+
+		initEffect(0);
+	}
+
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		StringTokenizer st = new StringTokenizer(br.readLine());
+		N = Integer.parseInt(st.nextToken());
+		Q = Integer.parseInt(st.nextToken());
+
+		StringBuilder sb = new StringBuilder();
+		int c;
+		while (Q-- > 0) {
+			st = new StringTokenizer(br.readLine());
+			int command = Integer.parseInt(st.nextToken());
+			switch (command) {
+				case 100:	// 사내 메신저 준비
+					init(st);
+					break;
+				case 200:	// 알림망 설정 (ON/OFF)
+					c = Integer.parseInt(st.nextToken());
+					toggleNotification(c);
+					break;
+				case 300:	// 권한 세기 변경
+					c = Integer.parseInt(st.nextToken());
+					int power = Integer.parseInt(st.nextToken());
+					changeAuthority(c, power);
+					break;
+				case 400:	// 부모 채팅방 교환
+					int c1 = Integer.parseInt(st.nextToken());
+					int c2 = Integer.parseInt(st.nextToken());
+					swapParent(c1, c2);
+					break;
+				case 500:	// 알림을 받을 수 있는 채팅방 수 조회
+					c = Integer.parseInt(st.nextToken());
+					sb.append(rooms[c].effect[0] - 1).append("\n");
+					break;
+			}
+		}
+		System.out.println(sb);
+	}
+}