#include<algorithm>
#include<stdio.h>

using namespace std;

int main()
{
	int v[801],n,i,j,r=0,k;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;i++)
		scanf("%d",&v[i]);
	sort(&v[1],&v[n+1]);
	for (i=1;i<n-1;i++)
	{
		k=i+2;
		for(j=i+1;j<n;j++)
		{
			while(k<=n && v[i]+v[j]>=v[k])
				++k;
			r+=k-1-j;
		}
	}
	printf("%d",r);
	return 0;
}