foo.cc: In function 'void gao(int, int, int)':
foo.cc:8:11: warning: unused variable 'b' [-Wunused-variable]
     int a,b,c=0,y=x;
           ^
foo.cc: In function 'void get_sg(int)':
foo.cc:16:13: warning: unused variable 'c' [-Wunused-variable]
     int a,b,c;
             ^
foo.cc: In function 'int main()':
foo.cc:42:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d",&b);
             ~~~~~^~~~~~~~~

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