#include <bits/stdc++.h>
using namespace std;
int main () {
	int N;
	cin >> N;
	using ll = long long;
	const int M = 2003;
	ll dp[M][M][4];
	ll ans = 0;
	for (auto& a : dp) {
		for (auto& b : a) {
			for (auto& c : b) {
				c = 0;
			}
		}
	}
	for (int i = 0; i < N; i ++) {
		int a;
		cin >> a;
		for (int k = 1; k <= 2000; k ++) {
			int a1 = a - (k + 11);
			if (1 <= a1 && a1 < M) {
				dp[a1][k][3] += dp[a1][k][2];
			}
			a1 = a - 10;
			if (1 <= a1 && a1 < M) {
				dp[a1][k][2] += dp[a1][k][1];
			}
			a1 = a - (k + 10);
			if (1 <= a1 && a1 < M) {
				dp[a1][k][1] += dp[a1][k][0];
			}
			dp[a][k][0] ++;
		}
	}
	for (int a = 1; a <= 2000; a ++) {
		for (int k = 1; k <= 2000; k ++) {
			ans += dp[a][k][3];
		}
	}
	cout << ans << endl;
}