foo.cc: In function 'int main()':
foo.cc:9:53: warning: unused variable 'c' [-Wunused-variable]
     int nx,ny,x,y,i,k,sum=0,nowx,nowy,head=1,tail=1,c;
                                                     ^

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