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

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

int sir[801], N;

int main()
{
    in >> N; int count = 0;
    for (int i = 1; i <= N; i++)
        in >> sir[i];
    sort(sir+1, sir+N+1);
    for (int i = 1; i < N-1; i++)
    {
        for (int j = i+1; j < N; j++)
        {
            int sum = sir[i]+sir[j];
            for (int k = j+1; k <= N; k++)
                if (sum >= sir[k]) ++count;
                else break;
        }
    }
    out << count;
    return 0;
}