#include<stdio.h>
#include<stdlib.h>

int n,a[802],i,j,k,nr;

int cmp(const void *a,const void *b)
{
	return (*(int*)a-*(int*)b);
}

int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	
	scanf("%d",&n);
	
	for(i=1;i<=n;i++)
		scanf("%d",&a[i]);
	
	qsort(a+1,n,sizeof(int),cmp);
	
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<=n-1;j++)
			for(k=j+1;k<=n;k++)
			{
				if(a[i]+a[j]>=a[k])
					nr++;
				else
					break;
			}
			
	printf("%d",nr);
	
	return 0;
}