#include<cstdio>
using namespace std;
int n,t[805],rez;


void bs()
{int ok,j,a;
 do
 {ok=0;
  for(j=0;j<n-1;++j)
	  if(t[j]>t[j+1])
	  {a=t[j];
	   t[j]=t[j+1];
	   t[j+1]=a;
	   ok=1;
	  }
 }while(ok);
}

int main()
{FILE* i=fopen("nrtri.in","r");
 FILE* o=fopen("nrtri.out","w");
 fscanf(i,"%d",&n);
 for(int k=0;k<n;++k)fscanf(i,"%d",&t[k]);
 bs();
 int j,l;
 for(int k=0;k<n-2;++k)
	 for(j=k+1;j<n-1;++j)
		for(l=j+1;l<n && t[k]+t[j]>=t[l];++l)
			++rez;
 fprintf(o,"%d",rez);
 
 fclose(i);
 fclose(o); 
 return 0;
}