foo.cc: In function 'int main()':
foo.cc:6:12: warning: unused variable 'i' [-Wunused-variable]
  int xo,yo,i,j,gcd = 0,lcm = 0,k1,k2,num = 0;
            ^
foo.cc:6:16: warning: unused variable 'gcd' [-Wunused-variable]
  int xo,yo,i,j,gcd = 0,lcm = 0,k1,k2,num = 0;
                ^~~
foo.cc:6:24: warning: unused variable 'lcm' [-Wunused-variable]
  int xo,yo,i,j,gcd = 0,lcm = 0,k1,k2,num = 0;
                        ^~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。