#include<cstdio>
#include<algorithm>
using namespace std;

int n,v[810],i,j,k,nr;

void read(),solve();

int main()
{
	read();
	solve();
	
	return 0;
}

void read()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;i++)scanf("%d",&v[i]);
}

void solve()
{
	sort(v+1,v+n+1);
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<=n-1;j++)
		{
			k=j+1;
			while((v[i]+v[j])>=v[k]&&k<=n)k++;
			nr+=k-j-1;
		}
	printf("%d",nr);
}