#include <fstream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <set>
#include <cstring>
#include <queue>
#include <cmath>
#define ll long long
#define ld long double

using namespace std;

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

const int NMAX = 800;

int n, answer;
int a[NMAX + 1];

int CautBin(int start, int value) {
    int left = start, right = n, answer = -1;
    while(left <= right) {
        int mid = (left + right) / 2;
        if(a[mid] <= value) {
            answer = mid;
            left = mid + 1;
        }
        else {
            right = mid - 1;
        }
    }
    return answer;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    cin >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    sort(a + 1, a + n + 1);
    for(int i = 1; i <= n - 2; i++) {
        for(int j = i + 1; j <= n - 1; j++) {
            int sum = a[i] + a[j];
            int pos = CautBin(j + 1, sum);
            if(pos != -1) {
                answer += pos - (j + 1) + 1;
            }
        }
    }
    cout << answer << '\n';
    return 0;
}