foo.cc: In function 'int main()':
foo.cc:9:13: warning: variable 'c' set but not used [-Wunused-but-set-variable]
     int n,i,c,j,k,l,tip,dir,begin,ans=0,len,len1;
             ^
foo.cc:10:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~

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