//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 0xccccccc;
const ll LINF = 0xcccccccccccccccLL;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}



//head



int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n;
	cin >> n;
	vector<ll> a(n);
	rep(i, n) cin >> a[i];
	sort(all(a));
	vector<array<ll, 2>> dp(n, {0, 1});
	ll ans = 0;
	rep(i, n) {
		if(dp[i][0] != 0) {
			ll z = dp[i][0]*dp[i][1];
			if(i != n-1 and a[i+1] == a[i]+1) {
				dp[i+1][1] += z;
			}
			else if(i != n-1 and a[i+1] == a[i]+2) {
				dp[i+1][0] += z;
			}
			else {
				ans += z;
			}
		}
		if(i != n-1 and a[i+1] == a[i]+1) {
			ll z = dp[i][1];
			if(i != n-2 and a[i+2] == a[i]+2) {
				dp[i+2][1] += z;
			}
			else if(i != n-2 and a[i+2] == a[i]+3) {
				dp[i+2][0] += z;
			}
			else {
				ans += z;
			}
		}
	}
	rep(i, n) ans += dp[i][0] + dp[i][1];
	cout << ans << endl;
}