/in/foo.cc: In function 'int main()':
/in/foo.cc:17:17: error: 'n' was not declared in this scope
  for(int i=1;i<=n;i++){
                 ^
/in/foo.cc:24:31: error: 'calc' was not declared in this scope
             ans=ans*calc(i,tot)%MOD;
                               ^
/in/foo.cc:28:22: error: 'calc' was not declared in this scope
      ans=ans*calc(a,1)%MOD;
                      ^