func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     int n, m, i, j, k, ct;     bool swapped = false;     cin >> n >> m;     if (n < m) {       swap(n, m);       swapped = true;     }     vector<vector<int>> ans(n, vector<int>(m, -1));     ct = 0;     if (m == 1) {       for (i = 1; i < n; i += 2) ans[i][0] = ++ct;       for (i = 0; i < n; i += 2) ans[i][0] = ++ct;     } else {       for (i = 0; i < n; i++) {         for (j = i % 2; j < m; j += 2) ans[i][j] = ++ct;       }       for (i = 0; i < n; i++) {         for (j = 1 - (i % 2); j < m; j += 2) ans[i][j] = ++ct;       }     }     bool solved = true;     for (i = 0; i < n; i++) {       for (j = 0; j < m; j++) {         if ((i < n - 1) && (abs(ans[i][j] - ans[i + 1][j]) == 1)) solved = false;         if ((j < m - 1) && (abs(ans[i][j] - ans[i][j + 1]) == 1)) solved = false;       }     }     if (!solved)       cout <<  -1 n ;     else {       if (!swapped) {         for (i = 0; i < n; i++) {           for (j = 0; j < m; j++) cout << ans[i][j] <<    ;           cout <<   n ;         }       } else {         for (j = 0; j < m; j++) {           for (i = 0; i < n; i++) cout << ans[i][j] <<    ;           cout <<   n ;         }       }     }     return 0;   }   