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

int v[800],n;

void citeste()
{
	int i,t;
	freopen("nrtri.in","r",stdin);
	scanf("%d",&n);
	//v=(int*)malloc(n*sizeof(int));
	for(i=0;i<n;i++)
		scanf("%d",&v[i]);
	for(i=1;i<n;i++)
		if(v[i-1]>v[i])
		{	t=v[i],v[i]=v[i-1],v[i-1]=t;
			i=0;
		}
}

int main()
{       int i,j,k;
	int count=0;
	citeste();

	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])	count++;
		else break;
	freopen("nrtri.out","w",stdout);
	printf("%d\n",count);
	//fclose(stdout);
	//free(v);
	return 0;
}