#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int main()
{
    int n,i,v[802],j,h,nr=0;
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
    {
        int a=v[i];
        for(j=i+1;j<=n-1;j++)
        {
            int s=a+v[j];
            h=j+1;
            while(s>=v[h]&&h<=n)
            {
                nr++;
                h++;
            }
        }
    }
    g<<nr;
    return 0;
}