func_code_string: #include <bits/stdc++.h>   using namespace std;   const int nax = 505;   int n;   char grid[nax][nax];   int cc[nax][nax];   int cc_size[nax * nax];   int when_added[nax * nax];   const int dx[4] = {-1, 1, 0, 0};   const int dy[4] = {0, 0, -1, 1};   const char EMPTY =  . ;   bool inside(int x, int y) { return 0 <= min(x, y) && max(x, y) < n; }   void dfs(int x, int y, int which_cc) {     cc[x][y] = which_cc;     ++cc_size[which_cc];     for (int i = 0; i < 4; ++i) {       int x2 = x + dx[i];       int y2 = y + dy[i];       if (inside(x2, y2) && grid[x2][y2] == EMPTY && cc[x2][y2] == 0)         dfs(x2, y2, which_cc);     }   }   void add(int x, int y, int& answer, int current_time) {     if (inside(x, y) && grid[x][y] == EMPTY) {       int id = cc[x][y];       if (when_added[id] != current_time) {         when_added[id] = current_time;         answer += cc_size[id];       }     }   }   int main() {     int k;     scanf( %d%d , &n, &k);     for (int i = 0; i < n; ++i) scanf( %s , grid[i]);     int how_many_cc = 0;     for (int x = 0; x < n; ++x)       for (int y = 0; y < n; ++y)         if (grid[x][y] == EMPTY && cc[x][y] == 0) dfs(x, y, ++how_many_cc);     int cur_time = 1;     int best_answer = 0;     for (int y_low = 0; y_low + k <= n; ++y_low) {       for (int x = 0; x < k; ++x)         for (int y = y_low; y < y_low + k; ++y) --cc_size[cc[x][y]];       for (int x_low = 0; x_low + k <= n; ++x_low) {         int answer = k * k;         for (int x = x_low; x < x_low + k; ++x) {           add(x, y_low - 1, answer, cur_time);           add(x, y_low + k, answer, cur_time);         }         for (int y = y_low; y < y_low + k; ++y) {           add(x_low - 1, y, answer, cur_time);           add(x_low + k, y, answer, cur_time);         }         ++cur_time;         best_answer = max(best_answer, answer);         if (x_low + k != n) {           for (int y = y_low; y < y_low + k; ++y) {             ++cc_size[cc[x_low][y]];             --cc_size[cc[x_low + k][y]];           }         }       }       for (int x = n - k; x < n; ++x)         for (int y = y_low; y < y_low + k; ++y) ++cc_size[cc[x][y]];     }     printf( %d , best_answer);     return 0;   }   