diff --git "a/Seol-JY/202511/21 BOJ G3 \353\202\230\353\250\270\354\247\200 \355\225\251.md\342\200\216" "b/Seol-JY/202511/21 BOJ G3 \353\202\230\353\250\270\354\247\200 \355\225\251.md\342\200\216"
new file mode 100644
index 00000000..1ffbbd49
--- /dev/null
+++ "b/Seol-JY/202511/21 BOJ G3 \353\202\230\353\250\270\354\247\200 \355\225\251.md\342\200\216"	
@@ -0,0 +1,34 @@
+```
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        
+        int N = Integer.parseInt(st.nextToken());
+        int M = Integer.parseInt(st.nextToken());
+        
+        long[] count = new long[M];
+        count[0] = 1;
+        
+        long prefixSum = 0;
+        st = new StringTokenizer(br.readLine());
+        
+        for (int i = 0; i < N; i++) {
+            prefixSum += Long.parseLong(st.nextToken());
+            int mod = (int) (prefixSum % M);
+            count[mod]++;
+        }
+        
+        long answer = 0;
+        for (int i = 0; i < M; i++) {
+            answer += count[i] * (count[i] - 1) / 2;
+        }
+        
+        System.out.println(answer);
+    }
+}
+
+```