/in/foo.cc: In function 'int gys(int, int)':
/in/foo.cc:11:9: warning: 'res' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return res;
         ^~~
/in/foo.cc: In function 'int gbs(int, int)':
/in/foo.cc:21:9: warning: 'res' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return res;
         ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:29:18: warning: 'res' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<Gbs<<" "<<Gys<<endl;
                  ^~~
/in/foo.cc:29:13: warning: 'res' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<Gbs<<" "<<Gys<<endl;
             ^~~