#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int n,a[803],nr;
int main()
{
    f>>n;
    for(int i=1; i<=n; i++) f>>a[i];
    sort(a+1,a+n+1);
    int i=1;
    while(i<n-1)
    {
        int j=i+2;
        while(a[j]<=a[i]+a[i+1] && j<=n) {nr++; j++;}
        i++;
    }
    g<<nr<<'\n';
    return 0;
}