/in/foo.cc: In function 'int main()':
/in/foo.cc:9:10: warning: unused variable 'r' [-Wunused-variable]
  int a,b,r,sum;
          ^
/in/foo.cc:9:12: warning: unused variable 'sum' [-Wunused-variable]
  int a,b,r,sum;
            ^