#include <bits/stdc++.h>

using namespace std;

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

int v[808];

int main()
{
    int n;
    fin >> n;
    for (int i=1;i<=n;++i){
        fin >> v[i];
    }
    sort(v+1,v+n+1);
    if (n<3){
        fout << 0;
    }else{
        int ans = 0;
        for (int i=1;i<=n-2;++i){
            for (int j=i+1;j<=n-1;++j){
                for (int k=j+1;k<=n;++k){
                    if (v[i]+v[j]>=v[k]) ans++;
                    else break;
                }
            }
        }
        fout << ans;
    }
    return 0;
}