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

#define X 801

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

int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	
	int a[X],n,i,j,l,sum,sol=0;
	
	scanf("%d",&n);
	for(i=0; i<n; ++i) scanf("%d",&a[i]);

	qsort(a,n,sizeof(a[0]),cmp);
	
	for(i=0; i<n-1; ++i)
		for(j=i+1; j<n; ++j)
		{
			sum=0;
			sum=a[i]+a[j];
			for(l=j+1; l<n; ++l)
				if(sum>=a[l]) ++sol; 
			             else break;
		}

	printf("%d",sol);

	return 0;
}