diff --git a/src/problems/from/number15900/Baekjoon_15991.java b/src/problems/from/number15900/Baekjoon_15991.java
new file mode 100644
index 0000000..e6e4a81
--- /dev/null
+++ b/src/problems/from/number15900/Baekjoon_15991.java
@@ -0,0 +1,50 @@
+package problems.from.number15900;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+public class Baekjoon_15991 {
+	
+	public static int toInt(String s) {
+		return Integer.parseInt(s);
+	}
+	
+	public static void main(String[] args) throws IOException {
+		
+		InputStreamReader isr = new InputStreamReader(System.in);
+		BufferedReader br = new BufferedReader(isr);
+		
+		int cases = toInt(br.readLine());
+		int[] memoization = new int[100001];
+		int modNumber = 1000000009;
+		memoization[0] = 0;
+		memoization[1] = 1;
+		memoization[2] = 2;
+		memoization[3] = 4;
+		
+		for (int i=4; i<100001; i++) {
+			for (int j=1; j<4; j++) {
+				memoization[i] += memoization[i-j];
+			}
+		}
+		
+		for (int i=0; i<cases; i++) {
+			int number = toInt(br.readLine());
+			int temp = 0;
+			for (int j=0; j<4; j++) {
+				if ((number-j)%2 == 0) {
+					temp += memoization[(number-j)/2];
+					temp %= modNumber;
+				}
+			}
+			System.out.println(temp % modNumber);
+		}
+	}
+}
+/*
+3
+4
+7
+100
+*/