View Compilation Error

0_0_37005362_3850.cpp: In function 'int main()':
0_0_37005362_3850.cpp:16:3: error: 'c' was not declared in this scope
   c[i][0] = 1;
   ^
0_0_37005362_3850.cpp:17:23: error: 'i' was not declared in this scope
   for(int j = 1; j <= i; j ++) {
                       ^
0_0_37005362_3850.cpp:19:4: error: 'c' was not declared in this scope
    c[i][j] = (long long) (c[i - 1][j - 1] + c[i - 1][j]) % mod;
    ^
0_0_37005362_3850.cpp:24:40: error: 'c' was not declared in this scope
   if(f + b - 2 < n) ans = (long long) (c[b + f - 2][f - 1] * s[n - 1][b + f - 2]) % mod;
                                        ^