#include<stdio.h>
int v[800],n,i,j,k,q;
FILE *in,*out;
int main()
{
	in=fopen("nrtri.in","r");
	fscanf(in,"%d",&n);
	for(i=0;i<n;i++)fscanf(in,"%d",&v[i]);
	fclose(in);
	for(i=0;i<=n-3;i++)
	for(j=i+1;j<=n-2;j++)
	for(k=j+1;k<=n-1;k++)
	if(v[i]<=v[j]+v[k]&&v[j]<=v[i]+v[k]&&v[k]<=v[i]+v[j])q++;
	out=fopen("nrtri.out","w");
	fprintf(out,"%d",q);
	fclose(out);
}