diff --git a/code_study/Baekjoon/c/21736.c b/code_study/Baekjoon/c/21736.c
new file mode 100644
index 0000000..9652ca9
--- /dev/null
+++ b/code_study/Baekjoon/c/21736.c
@@ -0,0 +1,62 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main() {
+    int N, M;
+    scanf("%d %d",&N, &M);
+    
+    char** campus = (char**)malloc(sizeof(char*)*N);
+    int** visited = (int**)malloc(sizeof(int*)*N);
+    for(int i=0; i<N; i++) {
+        campus[i] = (char*)malloc(sizeof(char)*(M+1));
+        visited[i] = (int*)malloc(sizeof(int)*M);
+        memset(visited[i], 0, sizeof(int)*M);
+    }
+
+    int* queueX = (int*)malloc(sizeof(int)*(N*M));
+    int* queueY = (int*)malloc(sizeof(int)*(N*M));
+    
+    for(int n=0; n<N; n++){
+        scanf("%s",campus[n]);
+        for(int m=0; m<M; m++){
+            if(campus[n][m] == 'I'){
+                queueY[0] = n;
+                queueX[0] = m;
+                visited[n][m] = 1;
+            }
+        }
+    }
+    int front = 0, rear = 1, friendCount = 0;
+    int dx[4] = {-1,1,0,0};
+    int dy[4] = {0,0,-1,1};
+    
+    while(front<rear){
+        int x = queueX[front];
+        int y = queueY[front];
+        front++;
+        for(int i=0; i<4; i++){
+            int nx = x + dx[i];
+            int ny = y + dy[i];
+            if(nx<0 || nx>=M || ny<0 || ny>=N || visited[ny][nx] || campus[ny][nx] == 'X') continue;
+            visited[ny][nx] = 1;
+            queueX[rear] = nx;
+            queueY[rear] = ny;
+            rear++;
+            if(campus[ny][nx] == 'P') friendCount++;
+        }
+    }
+
+    if(friendCount) printf("%d\n",friendCount);
+    else printf("TT\n");
+
+    for(int i=0; i<N; i++){
+        free(campus[i]);
+        free(visited[i]);
+    }
+    free(campus);
+    free(visited);
+    free(queueX);
+    free(queueY);
+    return 0;
+}
\ No newline at end of file