#include <iostream>
#include <fstream>

using namespace std;

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



int main()
{
    int n, a[806];
    int nr = 0;
    f>>n;
    for(int i = 1;i <= n;i ++)
        f>>a[i];
    for(int i = 1;i <= n - 2;i++)
        for(int j = i + 1;j <= n - 1;j++)
            for(int k = j + 1;k <= n;k++){
                if(a[i] + a[j] >= a[k] && a[i] + a[k] >= a[j] && a[j] + a[k] >=a[i])
                    nr++;

                }

    g<<nr;
    return 0;
}