/in/foo.cc: In function 'int main()':
/in/foo.cc:20:6: warning: unused variable 'a1' [-Wunused-variable]
  int a1,b1,ax,bx;
      ^~
/in/foo.cc:20:9: warning: unused variable 'b1' [-Wunused-variable]
  int a1,b1,ax,bx;
         ^~
/in/foo.cc:20:12: warning: unused variable 'ax' [-Wunused-variable]
  int a1,b1,ax,bx;
            ^~
/in/foo.cc:20:15: warning: unused variable 'bx' [-Wunused-variable]
  int a1,b1,ax,bx;
               ^~
/in/foo.cc: In function 'int gys(int, int)':
/in/foo.cc:15:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^