diff --git a/TangDou/LanQiaoBei/LanQiao14STEMA202301/BC3.cpp b/TangDou/LanQiaoBei/LanQiao14STEMA202301/BC3.cpp
index b28c192..62c2e07 100644
--- a/TangDou/LanQiaoBei/LanQiao14STEMA202301/BC3.cpp
+++ b/TangDou/LanQiaoBei/LanQiao14STEMA202301/BC3.cpp
@@ -13,7 +13,7 @@ int main() {
     for (int i = 0; i < n; i++) {
         cin >> a[i];
         sum += a[i];
-        a[i + n] = a[i]; // 破环成链, 0 1 2-->a[3]=a[0],a[4]=a[1],a[5]=a[2]
+        a[i + n] = a[i]; // 破环成链
     }
     avg = sum / n; // 平均数
     int mi = INF;  // 最少次数，给初始值最大
diff --git a/TangDou/LanQiaoBei/LanQiao14STEMA202301/BC4.cpp b/TangDou/LanQiaoBei/LanQiao14STEMA202301/BC4.cpp
new file mode 100644
index 0000000..8bf7aa8
--- /dev/null
+++ b/TangDou/LanQiaoBei/LanQiao14STEMA202301/BC4.cpp
@@ -0,0 +1,33 @@
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 31;
+char a[N][N];
+int n, m, cnt;
+
+int main() {
+    cin >> n >> m;
+
+    for (int i = 0; i < n; i++)
+        for (int j = 0; j < m; j++)
+            cin >> a[i][j];
+
+    for (int e = 2; e <= min(m, n); e++) {     // 枚举每个小正方形的边长
+        for (int i = 0; i <= n - e; i++) {     // 起点i
+            for (int j = 0; j <= m - e; j++) { // 起点j
+                bool f = true;
+                for (int x = 0; x < e; x++) { // 遍历正方形中所有的其它位置，判断是不是与左上角的一致
+                    for (int y = 0; y < e; y++) {
+                        if (a[i][j] != a[i + x][j + y]) {
+                            f = false;
+                            break;
+                        }
+                    }
+                    if (!f) break;
+                }
+                if (f) cnt++;
+            }
+        }
+    }
+    cout << cnt << endl;
+    return 0;
+}
\ No newline at end of file