#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
    ll N; cin >> N;
    vector<ll>A(N);
    ll Max = -1, Min = 100010;
    for (ll i = 0; i < N; i++) {
        cin >> A[i];
        Max = max(Max, A[i]);
        Min = min(Min, A[i]);
    }
    ll ans = 0;
    for (ll k = 1; k <= Max - Min; k++) {
        vector<vector<ll>>dp(N, vector<ll>(4, 0));
        dp[0][0] = 1;
        for (ll i = 1; i < N; i++) {
            dp[i][0] = 1;
            for (ll j = 0; j < i; j++) {
                if (A[j] + 10 + k == A[i]) dp[i][1] += dp[j][0];
                if (A[j] - k == A[i]) dp[i][2] += dp[j][1];
                if (A[j] + k + 1 == A[i]) dp[i][3] += dp[j][2];
            }
        }
        for (ll i = 0; i < N; i++) {
            ans += dp[i][3];
        }
    }
    cout << ans << endl;
}