answer.code: In function ‘void calc(int, int, int)’:
answer.code:6:20: error: ‘a’ was not declared in this scope
    6 |         int last = a;
      |                    ^
answer.code:7:29: error: ‘b’ was not declared in this scope
    7 |         for (int i = a; i < b; i++) {
      |                             ^
answer.code:8:22: error: ‘F’ was not declared in this scope
    8 |                 if (!F[x][i]) continue;
      |                      ^
answer.code:9:31: error: ‘res’ was not declared in this scope
    9 |                 if (i > last) res = max (res, dp[y1][y2][last][i] + i - last);
      |                               ^~~
answer.code:12:13: error: ‘b’ was not declared in this scope
   12 |         if (b > last) res = max (res, dp[y1][y2][last][b] + b - last);
      |             ^
answer.code:12:23: error: ‘res’ was not declared in this scope
   12 |         if (b > last) res = max (res, dp[y1][y2][last][b] + b - last);
      |                       ^~~