#include<stdio.h>
#define N 1000
int n,v[N];
void read()
{
	int i;
	scanf("%d",&n);
	for(i=0;i<n;i++)
		scanf("%d",&v[i]);
}
void solve()
{
	int i,j,k,nr=0;
	for(i=0;i<n-2;i++)
		for(j=i+1;j<n-1;j++)
			for(k=j+1;k<n;k++)
				if(v[i]+v[j]>=v[k]&&v[i]+v[k]>=v[j]&&v[j]+v[k]>=v[i])
					nr++;
	printf("%d\n",nr);
}
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	read();
	solve();
	return 0;
}