#include<bits/stdc++.h>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int n, ans, v[888];

int main() {
    fin >> n;
    for(int i=1;i<=n;i++)
        fin >> v[i];

    sort(v+1,v+n+1);

    for(int i=1; i<=n-2; ++i)
        for(int j=i+1; j<=n-1; ++j) {
            int sq = j + 1;
            while(v[i] + v[j] >= v[sq] && sq<=n) {
                ++sq;
                ++ans;
            }
        }

    fout << ans << '\n';

    return 0;
}