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

using namespace std;

int v[810],n;

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