#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int main()
{
    int v[802], n, ans = 0;
    cin >> n;
    for(int i=1;i<=n;i++) cin >> v[i];
    sort(v+1, v+n+1);
    for(int a=1;a<=n-2;a++)
    {
        int c = a + 2;
        for(int b=a+1;b<=n-1;b++){
            while(c<=n and v[a]+v[b]>=v[c])
                c++;
            ans = ans + c - b - 1;
        }
    }
    cout << ans;
    return 0;
}