//ALEX ENACHE

#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <unordered_map>
#include <time.h>
#include <iomanip>
#include <deque>
#include <math.h>
#include <assert.h>
#include <stack>
#include <bitset>
#include <random>

using namespace std;

//-----------------------------------------------------------------

#include <fstream>

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

int v[805];

int main() {

	int n;
	cin >> n;

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

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

	int ans = 0;

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

	cout << ans;

	return 0;
}