func_code_string: #include <bits/stdc++.h>   using namespace std;   int a[1000][1000];   int b[1000][1000];   int f[1000][1000];   int sum[4][1000][1000];   int dx[4] = {0, 0, -1, 1};   int dy[4] = {-1, 1, 0, 0};   int gcd(int a, int b) {     if (a % b == 0) {       return b;     } else {       return gcd(b, a % b);     }   }   int main() {     int n, m, x = -1, y = -1, g = -1, i, j, k;     vector<int> v;     vector<int> w;     scanf( %d %d , &n, &m);     for (i = 0; i < n; i++) {       for (j = 0; j < m; j++) {         scanf( %d , &a[i][j]);       }     }     for (i = 0; i < n; i++) {       for (j = 0; j < m; j++) {         if (a[i][j] == 1) {           if (j == 0) {             sum[0][i][j] = 1;           } else {             sum[0][i][j] = sum[0][i][j - 1] + 1;           }         } else {           sum[0][i][j] = 0;         }       }       for (j = m - 1; j >= 0; j--) {         if (a[i][j] == 1) {           sum[1][i][j] = sum[1][i][j + 1] + 1;         } else {           sum[1][i][j] = 0;         }       }     }     for (i = 0; i < m; i++) {       for (j = 0; j < n; j++) {         if (a[j][i] == 1) {           if (j == 0) {             sum[2][j][i] = 1;           } else {             sum[2][j][i] = sum[2][j - 1][i] + 1;           }         } else {           sum[2][j][i] = 0;         }       }       for (j = n - 1; j >= 0; j--) {         if (a[j][i] == 1) {           sum[3][j][i] = sum[3][j + 1][i] + 1;         } else {           sum[3][j][i] = 0;         }       }     }     for (i = 0; i < n; i++) {       for (j = 0; j < m; j++) {         if (a[i][j] == 1 && x == -1) {           x = i;           y = j;         }       }     }     for (i = 0; i < n; i++) {       int x = 0;       for (j = 0; j < m; j++) {         if (a[i][j] == 0) {           if (x > 1) {             if (g == -1) {               g = x - 1;             } else {               g = gcd(g, x - 1);             }           }           x = 0;         } else {           x++;         }       }       if (x > 1) {         if (g == -1) {           g = x - 1;         } else {           g = gcd(g, x - 1);         }       }     }     for (i = 0; i < m; i++) {       int x = 0;       for (j = 0; j < n; j++) {         if (a[j][i] == 0) {           if (x > 1) {             if (g == -1) {               g = x - 1;             } else {               g = gcd(g, x - 1);             }           }           x = 0;         } else {           x++;         }       }       if (x > 1) {         if (g == -1) {           g = x - 1;         } else {           g = gcd(g, x - 1);         }       }     }     for (i = 2; i <= g; i++) {       if (g % i == 0) v.push_back(i);     }     for (i = 0; i < v.size(); i++) {       int c1 = 0;       queue<pair<int, int> > q;       for (j = 0; j < n; j++) {         for (k = 0; k < m; k++) {           b[j][k] = f[j][k] = 0;         }       }       f[x][y] = 1;       q.push(make_pair(x, y));       while (!q.empty()) {         int x = q.front().first;         int y = q.front().second;         int c = 0;         q.pop();         b[x][y] = 1;         for (j = 0; j < 4; j++) {           if (sum[j][x][y] <= v[i]) continue;           c++;           for (k = 1; k <= v[i]; k++) b[x + dx[j] * k][y + dy[j] * k] = 1;           if (f[x + dx[j] * v[i]][y + dy[j] * v[i]] == 1) continue;           f[x + dx[j] * v[i]][y + dy[j] * v[i]] = 1;           q.push(make_pair(x + dx[j] * v[i], y + dy[j] * v[i]));         }         if (c & 1) c1++;       }       if (c1 <= 2) {         int f1 = 0;         for (j = 0; j < n; j++) {           for (k = 0; k < m; k++) {             if (a[j][k] != b[j][k]) {               f1 = 1;               break;             }           }         }         if (f1 == 0) w.push_back(v[i]);       }     }     if (w.size() == 0) {       puts( -1 );       return 0;     }     for (i = 0; i < w.size(); i++) {       if (i > 0) putchar(   );       printf( %d , w[i]);     }     puts(  );     return 0;   }   