#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;
	for(vector<int>::iterator i=v.begin();i!=v.end();++i) {
		for(vector<int>::iterator j=i+1;j!=v.end();++j) {
			vector<int>::iterator x = upper_bound(j+1,v.end(),*i + *j);
			x--;
			ans += (x - j);
		}
	}
	cout << ans << '\n';


	return 0;
}