#include <algorithm>
#include <iostream>
#include <fstream>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[805];

int main()
{
    int n;
    in>>n;
    for(int i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+n+1);
    int nr=0;
    /// 4
    /// 2 3 4 7


    /// a = 2 b = 3
    /// c < 5
    for(int i=1;i<=n;i++)
    {
        for(int j=i+1;j<=n;j++)
        {
            int a = v[i];
            int b = v[j];
            /** a + b > c
            v[poz] < a + b*/

            int st=j+1,dr=n;
            int rez=0;
            while(st<=dr)
            {
                int mid=(st+dr)/2;
                if(v[mid] <= a + b) {
                    rez = mid;
                    st = mid + 1;
                }
                else
                    dr = mid - 1;
            }
            if(rez)
                nr += (rez - j);
        }
    }
    out<<nr;
    return 0;
}