Language: C++

#include <algorithm>
#include <cmath>
#include <climits>

using namespace std;

int main(){
        ios_base::sync_with_stdio(false);
        while(true){
                int r, c, q;
                cin >> r >> c >> q;
                if(r == 0 && c == 0 && q == 0){ break; }
                vector< vector<int> > grid(r, vector<int>(c));
                for(int i = 0; i < r; ++i){
                        for(int j = 0; j < c; ++j){ cin >> grid[i][j]; }
                }
                int dr = sqrt(r), dc = sqrt(c);
                vector< vector<int> > decomp(r, vector<int>(c, INT_MAX));
                for(int i = 0; i < r; ++i){
                        for(int j = 0; j < c; ++j){
                                int di = i / dr, dj = j / dc;
                                decomp[di][dj] = min(decomp[di][dj], grid[i][j]);
                        }
                }
                while(q--){
                        int r1, c1, r2, c2, i, j, answer = INT_MAX;
                        cin >> r1 >> c1 >> r2 >> c2;
                        for(i = r1; i <= r2; ++i){
                                if(i % dr == 0){ break; }
                                for(j = c1; j <= c2; ++j){ answer = min(answer, grid[i][j]); }
                        }
                        for(; i + dr - 1 <= r2; i += dr){
                                for(j = c1; j <= c2; ++j){
                                        if(j % dc == 0){ break; }
                                        for(int k = 0; k < dr; ++k){
                                                answer = min(answer, grid[i + k][j]);
                                        }
                                }
                                for(; j + dc - 1 <= c2; j += dc){
                                        answer = min(answer, decomp[i / dr][j / dc]);
                                }
                                for(; j <= c2; ++j){
                                        if(j % dc == 0){ break; }
                                        for(int k = 0; k < dr; ++k){
                                                answer = min(answer, grid[i + k][j]);
                                        }
                                }
                        }
                        for(; i <= r2; ++i){
                                if(i % dr == 0){ break; }
                                for(j = c1; j <= c2; ++j){ answer = min(answer, grid[i][j]); }
                        }
                        cout << answer << endl;
                }
        }
        return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:9: error: 'ios_base' has not been declared
    8 |         ios_base::sync_with_stdio(false);
      |         ^~~~~~~~
a.cc:11:17: error: 'cin' was not declared in this scope
   11 |                 cin >> r >> c >> q;
      |                 ^~~
a.cc:4:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    3 | #include <climits>
  +++ |+#include <iostream>
    4 | 
a.cc:13:17: error: 'vector' was not declared in this scope
   13 |                 vector< vector<int> > grid(r, vector<int>(c));
      |                 ^~~~~~
a.cc:4:1: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
    3 | #include <climits>
  +++ |+#include <vector>
    4 | 
a.cc:13:32: error: expected primary-expression before 'int'
   13 |                 vector< vector<int> > grid(r, vector<int>(c));
      |                                ^~~
a.cc:15:60: error: 'grid' was not declared in this scope
   15 |                         for(int j = 0; j < c; ++j){ cin >> grid[i][j]; }
      |                                                            ^~~~
a.cc:18:32: error: expected primary-expression before 'int'
   18 |                 vector< vector<int> > decomp(r, vector<int>(c, INT_MAX));
      |                                ^~~
a.cc:22:33: error: 'decomp' was not declared in this scope
   22 |                                 decomp[di][dj] = min(decomp[di][dj], grid[i][j]);
      |                                 ^~~~~~
a.cc:22:70: error: 'grid' was not declared in this scope
   22 |                                 decomp[di][dj] = min(decomp[di][dj], grid[i][j]);
      |                                                                      ^~~~
a.cc:30:81: error: 'grid' was not declared in this scope
   30 |                                 for(j = c1; j <= c2; ++j){ answer = min(answer, grid[i][j]); }
      |                                                                                 ^~~~
a.cc:36:70: error: 'grid' was not declared in this scope
   36 |                                                 answer = min(answer, grid[i + k][j]);
      |                                                                      ^~~~
a.cc:40:62: error: 'decomp' was not declared in this scope
   40 |                                         answer = min(answer, decomp[i / dr][j / dc]);
      |                                                              ^~~~~~
a.cc:45:70: error: 'grid' was not declared in this scope
   45 |                                                 answer = min(answer, grid[i + k][j]);
      |                                                                      ^~~~
a.cc:51:81: error: 'grid' was not declared in this scope
   51 |                                 for(j = c1; j <= c2; ++j){ answer = min(answer, grid[i][j]); }
      |                                                                                 ^~~~
a.cc:53:25: error: 'cout' was not declared in this scope
   53 |                         cout << answer << endl;
      |                         ^~~~
a.cc:53:25: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:53:43: error: 'endl' was not declared in this scope
   53 |                         cout << answer << endl;
      |                                           ^~~~
a.cc:4:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
    3 | #include <climits>
  +++ |+#include <ostream>
    4 |