#include<cstdio>

int n,v[801];

int caut1(int x)
{
	int i,pas=1<<16;
	for(i=0;pas!=0;pas/=2)
		if(i+pas<=n && v[i+pas]<=x)
			i+=pas;
	return i;
}

int main()
{
	int i,j,aux,k,r=0;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;++i)
		scanf("%d",&v[i]);
	for(i=1;i<n;++i)
	{
		for(j=i+1;j<=n;++j)
		{
			if(v[i]>v[j])
			{
				aux=v[i];
				v[i]=v[j];
				v[j]=aux;
			}
		}
	}
	for(i=1;i<n;++i)
	{
		for(j=i+1;j<=n;++j)
		{
			k=caut1(v[i]+v[j]);
			if(k>j)
				r+=k-j;
		}
	}
	printf("%d\n",r);
	return 0;
}