#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;

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

int n;
int v[8001],cnt;

int main()
{
    in>>n;
    for(int i = 1; i<=n; i++)
    {
        in>>v[i];
    }
    sort(v+1,v+n+1);
    for(int start=1; start<=n-2; start++)
        for(int betisor2=start+1; betisor2<=n-1; betisor2++)
            for(int betisor3=betisor2+1; betisor3<=n && v[betisor3]<=v[start]+v[betisor2]; betisor3++)
                cnt++;
    out<<cnt;
    return 0;
}