#include <bits/stdc++.h>

using namespace std;

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

int main()
{
    int n, v[800], cnt=0, k;
    fin >> n;
    for(int i=0; i<n; i++) {
        fin >> v[i];
    }
    sort(v, v+n);
    for(int i=0; i<n-1; i++) {
        k=1;
        //cout << "i=" << i << endl;
        for(int j=i+1; j+k<n; j++) {
            //cout << "j=" << j << endl;
            if(v[i]+v[j]<v[j+k]) {
                //cout << v[i] << " " << v[j] << " " << v[j+k] << endl;
                break;
            } else {
                cnt++;
                //cout << v[i] << "|" << v[j] << ",.,. " << v[j+k] << endl;
                k++;
            }
        }
    }
    fout << cnt;
    return 0;
}