#include <fstream>
#include <algorithm>
using namespace std;
const int N = 801;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int v[N];
const int L = 9;
int main()
{
    int n,i,j,pas,max = 0,r,s=0,k;
    cin >> n;
    k = 0;
    pas = 1 << L;
    for(i=1; i<=n; i++)
    {
        cin >> v[i];
    }
    sort(v+1,v+n+1);
    for(i=1; i<=n; i++)
    {
        for(j=i+1; j <=n; j++)
        {
            k = j;
            while(pas!=0)
            {
                if(k+pas<=n &&  v[k+pas] <= v[i] + v[j])
                    k+=pas;
                pas /= 2;
            }
            s += k -j;
        }

    }
    cout << s;



    return 0;
}