foo.cc: In function ‘int main()’:
foo.cc:18:28: error: expected primary-expression before ‘)’ token
   18 |                         if()
      |                            ^
foo.cc:19:9: error: expected primary-expression before ‘}’ token
   19 |         }
      |         ^
foo.cc:21:2: error: expected ‘}’ at end of input
   21 | }
      |  ^
foo.cc:3:11: note: to match this ‘{’
    3 | int main(){
      |           ^
foo.cc:5:17: warning: unused variable ‘sum’ [-Wunused-variable]
    5 |         int n,m,sum=0;
      |                 ^~~