#include<fstream>
#include<algorithm> 
using namespace std;
 
int n, a[801], sol;
 
int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    f >> n;
    for (int i = 1; i <= n; i++)
        f >> a[i];
    sort (a + 1, a + n + 1);
 
    for (int i = 1; i <= n - 2; i++)
        for (int j = i + 1; j <= n - 1; j++)
            for (int k = j + 1; k <= n && a[i] + a[j] >= a[k]; k++)
                sol++;
    g << sol << '\n';
    return 0;
}