#include<bits/stdc++.h>

#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
#define sz size
#define pb push_back
#define mp make_pair
#define bg begin
#define nd end
using namespace std;

#define int long long

const int maxn = 100003;
const int maxk = 1003;

int n;
vector<int> v;

int32_t main(){

	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);

	ios_base::sync_with_stdio(false);
	cin.tie(0);

	cin >> n;
	for(int i=0;i<n;++i){
		v.pb(1);
		cin >> v[i];
	}

	sort(v.begin(),v.end());
	int ans = 0;
	vector<int>::iterator it_i=v.begin(),it_j;
	for(int i=0;i<n-1;++i) {
		it_j = it_i+1;
		for(int j=i+1;j<n;++j) {
			vector<int>::iterator it_x = upper_bound(it_j+1,v.end(),v[i] + v[j]);
			it_x--;
			ans += (it_x - it_j);
			++it_j;
		}
		++it_i;
	}
	cout << ans << '\n';


	return 0;
}