/in/foo.cc: In function 'long long int fact(int)':
/in/foo.cc:9:9: error: expected primary-expression before '=' token
   sum * = i ;
         ^
/in/foo.cc: In function 'long long int A(int, int)':
/in/foo.cc:17:9: error: expected primary-expression before '=' token
   sum * = i ;
         ^
/in/foo.cc: In function 'void C(int, int)':
/in/foo.cc:23:21: error: return-statement with a value, in function returning 'void' [-fpermissive]
  return A(n,m)/A(m,m);
                     ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:29:18: error: invalid operands of types 'void' and 'long long int' to binary 'operator*'
  LL ans = C(n,k) * A(n,k) * A(k,k) ;
           ~~~~~~~^~~~~~~~