/in/foo.cc: In function 'int main()':
/in/foo.cc:25:5: error: 'num' was not declared in this scope
     num++
     ^~~
/in/foo.cc:28:8: error: 'num' was not declared in this scope
  cout<<num;
        ^~~
/in/foo.cc:7:6: warning: unused variable 'sum' [-Wunused-variable]
  int sum=0;
      ^~~