#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int v[801],i,n,nr=0,j;
int main()
{
    f>>n;
    for(i=1; i<=n; i++) f>>v[i];
    sort(v+1,v+n+1);
    for(i=1; i<=n-2; i++)
        for(j=i+1; j<=n-1; j++)
        nr=nr+upper_bound(v+1,v+n+1,v[i]+v[j])-v-j-1;
        g<<nr;
            return 0;
}