foo.cc: In function 'int main()':
foo.cc:23:19: warning: format '%lld' expects argument of type 'long long int', but argument 2 has type 'int' [-Wformat=]
  printf("%lld",ans);
                   ^
foo.cc:16:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:19:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&x[i].a,&x[i].b);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:22:22: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   if(x[i].a>now)ans++,now=x[i].b;
                 ~~~~~^~~~~~~~~~~

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