#include <bits/stdc++.h>

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n, v[810];

int main()
{
    fin >> n;
    for(int i=1; i<=n; i++) fin >> v[i];
    sort(v+1, v+n+1);
    int rez = 0;
    for(int i=1; i<=n; i++) {
        for(int j=i+1; j<=n; j++) {
            int st = j + 1, dr = n;
            while(st <= dr) {
                int mid = (st + dr) / 2;
                if(v[i] + v[j] >= v[mid]) st = mid + 1;
                else dr = mid - 1;
            }
            rez += dr - j;
        }
    }
    fout << rez;

    return 0;
}