foo.cc: In function 'int main()':
foo.cc:20:15: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n,m;scanf("%d%d",&n,&m);
          ~~~~~^~~~~~~~~~~~~~
foo.cc:28:61: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1;i<=m;i++) scanf("%d%d",&query[i].l,&query[i].r),query[i].index=i;
                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

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