#include <fstream>

using namespace std;

ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
const int N = 800;
const int VAL_MAX = 30000;
int f[VAL_MAX + 1], v[N];
int main()
{
    int i, n, j, x, ap = 1, k, cnt = 0;
    cin >> n;
    for(i = 1; i <= n; i++)
    {
        cin >> x;
        f[x]++;
    }
    for(i = 0; i <= VAL_MAX; i++)
    {
        while(f[i] > 0)
        {
            v[ap++] = i;
            f[i]--;
        }
    }
    for(i = 1; i <= n - 2; i++)
    {
        k = i + 2;
        for(j = i + 1; j <= n - 1; j++)
        {
            while(v[i] + v[j] >= v[k] && k < n)
            {
                k++;
            }
            cnt += k - j;
            if(v[i] + v[j] < v[k])
                cnt--;
           // printf("%d %d %d %d %d %d\n", i, j, k, v[k], v[i], v[j]);
        }
    }
    cout << cnt;
    return 0;
}