foo.cc: In function 'int main()':
foo.cc:8:19: warning: unused variable 'j' [-Wunused-variable]
     int n,na,nb,i,j,sumA=0,sumB=0,pin=0;
                   ^
foo.cc:8:35: warning: unused variable 'pin' [-Wunused-variable]
     int n,na,nb,i,j,sumA=0,sumB=0,pin=0;
                                   ^~~

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