#include <bits/stdc++.h>

using namespace std;

ifstream in("nrtri.in");
ofstream out("nrtri.out");

const int NMAX = 1000;

int v[NMAX+2], Ans = 0;
int N;

int main()
{
    in >> N;
    for( int i = 1;  i <= N;  ++i ) in >> v[i];
    sort( v + 1, v + N + 1 );
    for( int a = 1;  a <= N;  ++a ) {
        int ind = 0;
        for( int i = 1;  i < a;  ++i ) {
            while( ind < N && v[ind + 1] <= v[a] + v[i] )
                ++ind;
            Ans += max(0, ind - a);
        }
    }
    out << Ans << '\n';
    return 0;
}