#include <fstream>
#include <algorithm>

using namespace std;

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

const int N = 801;
int v[N], n, r = 0, pas;

/*void tri(int n)
{
    pas = N;
    while(pas != 0)
    {
        if(r + pas <= n && v[pas] + v[pas+r] >= v[n])
        {
            r+=pas;
        }
        pas/=2;
    }
    out<<r;
}*/

void solve(int n)
{
    int x = 0;
    for(int i = 1; i < n-1; i++)
        for(int j = i+1; j <= n; j++)
            for(int k = j+1; k <= n && v[i] + v[j] >= v[k]; k++)
            {
                x++;
            }
    out<<x;
}

int main()
{
    in>>n;
    for(int i = 1; i <= n; i++)
        in>>v[i];
    sort(v + 1, v + n + 1);
    solve(n);
    return 0;
}