#include <fstream>
#include <iostream>
#include <algorithm>

using namespace std;

ifstream cin("nrtri.in");
ofstream cout("nrtri.out");

int n,v[1000],cnt;

int main()
{
    cin >> n;
    for(int i=1;i<=n;i++)
        cin >> v[i];
    sort(v+1,v+n+1);
    for(int i=1;i<=n-2;i++)
        for(int j=i+1;j<=n-1;j++)
            for(int h=j+1;h<=n;h++)
                if(v[h]<=v[i]+v[j])
                   cnt++;
                 else
                    break;
    cout << cnt;
}