#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");

int nr[60001], v[800];

int main()
{
    int i, n, rez, j;
    fi>>n;
    for(i=0;i<n;i++){
        fi>>v[i];
        nr[v[i]]++;
    }
    for(i=1;i<=60000;i++)
        nr[i]+=nr[i-1];
    sort(v,v+n);
    rez=0;
    for(i=0;i<n;i++)
        for(j=i+1;j<n;j++){
            rez=rez+(nr[v[i]+v[j]]-nr[v[j]-v[i]-1])-1;
            if(2*v[i]>=v[j])
                rez--;
        }
    fo<<rez/3;
    return 0;
}