/in/foo.cc: In function 'int main()':
/in/foo.cc:17:10: error: 'ans' was not declared in this scope
          ans = i;
          ^~~
/in/foo.cc:20:13: error: 'ans' was not declared in this scope
     cout << ans << endl;
             ^~~
/in/foo.cc:9:9: warning: unused variable 'i' [-Wunused-variable]
     int i, j, num=0;
         ^
/in/foo.cc:9:12: warning: unused variable 'j' [-Wunused-variable]
     int i, j, num=0;
            ^
/in/foo.cc:9:15: warning: unused variable 'num' [-Wunused-variable]
     int i, j, num=0;
               ^~~