#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
string file = "nrtri";
ifstream cin (file + ".in");
ofstream cout (file + ".out");
int n, v[100001];
inline int cbsus(int val)
{
    int st = 1, dr = n+1;
    while (dr != st + 1)
    {
        int mid = (st+dr)/2;
        if (v[mid] <= val)
        {
            st = mid;
        }
        else
        {
            dr = mid;
        }
    }
    return st;
}

inline int cbjos(int val)
{
    int st = 0, dr = n;
    while (dr!=st+1)
    {

        int mid = (st+dr)/2;
        if (v[mid] < val)
        {
            st = mid;
        }
        else
        {
            dr = mid;
        }
    }
    return dr;
}
int main()
{
    int c=0;
    cin >> n;
    for (int i=1; i<=n; i++)
        cin >> v[i];
    sort(v+1,v+n+1);
    for (int i=1; i<n; i++)
    {
        for (int j=i+1; j<=n; j++)
        {
            int l = cbsus(v[i]+v[j]) - j;
            if (l > 0)
                c+=l;
        }
    }
    cout << c;
    cin.close();
    cout.close();
    return 0;
}