#include<cstdio>

long i,j,k,n,numar;

int a[30001];

int triunghi(long b,long c,long d)
{
	
	if (a[b]+a[c]<a[d]) return 0;
	if (a[c]+a[d]<a[b]) return 0;
	if (a[d]+a[b]<a[c]) return 0;
	return 1;
	
}

int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%ld", &n);
	
	scanf("%ld%ld", &a[1], &a[2]);
	
	for (i=3;i<=n;++i)
	{
	scanf("%ld", &a[i]);
	for (j=1;j<i-1;j++)
		for (k=j+1;k<i;k++)
			if (triunghi(i,j,k)) numar++;
		
	}


	printf("%ld", numar);
	
	return 0;
	
}