foo.cc: In function 'int main()':
foo.cc:10:55: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long int' [-Wformat=]
  printf("%d", lower_bound(dp+1,dp+n+1,1000000000)-dp-1); 
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
foo.cc:6:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
foo.cc:7:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
                               ~~~~~^~~~~~~~~~~~~

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