#include <cstdio>
#include <algorithm>
using namespace std;
int v[805];


int main()
{
    FILE *in, *out;
    in = fopen("nrtri.in", "r");
    out = fopen("nrtri.out", "w");
    int i, solutie = 0, n, j, p;
    fscanf(in, "%d", &n);
    for (i = 1; i <= n; i++)
        fscanf(in, "%d", &v[i]);

    sort(v+1,v+n+1);

    for (int i=1; i<=n-2; i++)
        for (j = i + 1; j <= n - 1; j++)
            for (p = j + 1; p <= n; p++)
                if (v[i] + v[j] >= v[p])
                    solutie++;
                else
                    break;

    fprintf(out, "%d", solutie);
    return 0;
}