func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = 1e6 + 10;   int n, m;   vector<string> v(maxn);   int func(int x, vector<vector<int>> &s) {     vector<vector<int>> t(n + 3, vector<int>(m + 3, 0));     int i, j;     for (i = 1; i <= n - 2 * x; i++) {       for (j = 1; j <= m - 2 * x; j++)         if (s[i + 2 * x][j + 2 * x] - s[i - 1][j + 2 * x] - s[i + 2 * x][j - 1] +                 s[i - 1][j - 1] ==             (2 * x + 1) * (2 * x + 1)) {           t[i][j]++, t[i + 2 * x + 1][j + 2 * x + 1]++;           t[i][j + 2 * x + 1]--, t[i + 2 * x + 1][j]--;         }     }     for (i = 1; i <= n; i++)       for (j = 1; j <= m; j++) {         t[i][j] = t[i][j] + t[i - 1][j] + t[i][j - 1] - t[i - 1][j - 1];         if (v[i][j - 1] ==  X  && t[i][j] <= 0) return 0;       }     return 1;   }   int main() {     ios::sync_with_stdio(false);     cin.tie(0), cout.tie(0);     int i, j;     cin >> n >> m;     vector<vector<int>> s(n + 2, vector<int>(m + 2, 0));     for (i = 1; i <= n; i++) {       cin >> v[i];       for (j = 1; j <= m; j++)         s[i][j] =             s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + (v[i][j - 1] ==  X );     }     int l = 0, r = n, mid;     while (l < r) {       mid = (l + r + 1) >> 1;       if (func(mid, s))         l = mid;       else         r = mid - 1;     }     if (l == 0) {       cout << 0 <<   n ;       for (i = 1; i <= n; i++) cout << v[i] <<   n ;       return 0;     }     cout << l <<   n ;     vector<string> ans(n + 1, string(m,  . ));     for (i = 1; i <= n - 2 * l; i++) {       for (j = 1; j <= m - 2 * l; j++) {         if (s[i + 2 * l][j + 2 * l] - s[i - 1][j + 2 * l] - s[i + 2 * l][j - 1] +                 s[i - 1][j - 1] ==             (2 * l + 1) * (2 * l + 1))           ans[i + l][j + l - 1] =  X ;       }     }     for (i = 1; i <= n; i++) cout << ans[i] <<   n ;     return 0;   }   