View Compilation Error

0_0_32128689_4186.cpp: In function 'lint det(std::vector<std::vector<long long int> >, int, int)':
0_0_32128689_4186.cpp:31:69: error: 'MOD' was not declared in this scope
  for (int i = 0; i < n; i++) for (int j = 0; j < n; j++) a[i][j] %= MOD;
                                                                     ^