#include <stdio.h>
#include <algorithm>

using namespace std;

int v[900],i,j,n,nr,k;

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