/in/foo.cc: In function 'int main()':
/in/foo.cc:5:6: warning: unused variable 'a' [-Wunused-variable]
  int a,b,n,s=0;
      ^
/in/foo.cc:5:8: warning: unused variable 'b' [-Wunused-variable]
  int a,b,n,s=0;
        ^