#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));
        vector<vector<ll>>C(Max + 1, vector<ll>(4, 0));
        for (ll i = 0; i < N; i++) {
            dp[i][0] = 1;
            if (A[i] - 10 - k >= 1 && A[i] - 10 - k <= Max) {
                dp[i][1] += C[A[i] - 10 - k][0];
            }
            if (A[i] + k >= 1 && A[i] + k <= Max) {
                dp[i][2] += C[A[i] + k][1];
            }
            if (A[i] - k - 1 >= 1 && A[i] - k - 1 <= Max) {
                dp[i][3] += C[A[i] - k - 1][2];
            }
            for (ll j = 0; j < 4; j++) {
                C[A[i]][j] += dp[i][j];
            }
        }
        for (ll i = 0; i < N; i++) {
            ans += dp[i][3];
        }
    }
    cout << ans << endl;
}