#include <bits/stdc++.h>

using namespace std;
using ll = long long;
template <typename T>
using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using Graph = vector<vector<int>>;

const ll INF = 1LL << 60;

template <class T>
void chmax(T& a, T b) {
    if (b > a) a = b;
}
template <class T>
void chmin(T& a, T b) {
    if (b < a) a = b;
}

template <typename T, typename S>
std::ostream& operator<<(std::ostream& os, const pair<T, S>& x) noexcept {
    return os << "(" << x.first << ", " << x.second << ")";
}

template <typename T>
void print_vector(vector<T> a) {
    cout << '[';
    for (int i = 0; i < a.size(); i++) {
        cout << a[i];
        if (i != a.size() - 1) {
            cout << ", ";
        }
    }
    cout << ']' << endl;
}

class CumulativeSum {
   public:
    // コンストラクタ
    CumulativeSum();
    CumulativeSum(vector<ll>&);
    // コピーコンストラクタ
    CumulativeSum(const CumulativeSum&);
    ll query(int, int) const;
    ll original_elem(int) const;
    vector<ll> sum() const;
    ll lower_bound(int, ll) const;
    ll upper_bound(int, ll) const;

    // 演算子オーバーロード
    void operator=(const CumulativeSum&);

   private:
    vector<ll> sum_;
};

// コンストラクタ
CumulativeSum::CumulativeSum() {}

CumulativeSum::CumulativeSum(vector<ll>& a) {
    sum_ = vector<ll>(a.size() + 1, 0);
    for (int i = 0; i < a.size(); i++) {
        sum_[i + 1] = sum_[i] + a[i];
    }
}

// 区間 [left, right) の総和を求める
ll CumulativeSum::query(int left, int right) const {
    return sum_[right] - sum_[left];
}

// A[begin_idx] + ... + A[r-1] >= v であるような最小のrを求める
// (∀i A[i] >= 0 である場合のみ有効)
ll CumulativeSum::lower_bound(int begin_idx, ll v) const {
    auto left_it = next(sum_.begin(), begin_idx);
    ll dist = distance(sum_.begin(), std::lower_bound(left_it, sum_.end(),
                                                      v + query(0, begin_idx)));
    return dist;
}

// A[begin_idx] + ... + A[r-1] > v であるような最小のrを求める
// (∀i A[i] >= 0 である場合のみ有効)
ll CumulativeSum::upper_bound(int begin_idx, ll v) const {
    auto left_it = next(sum_.begin(), begin_idx);
    ll dist = distance(sum_.begin(), std::upper_bound(left_it, sum_.end(),
                                                      v + query(0, begin_idx)));
    return dist;
}

// 元の配列における index での値を得る
ll CumulativeSum::original_elem(int index) const {
    return sum_[index + 1] - sum_[index];
}

vector<ll> CumulativeSum::sum() const { return sum_; }

// 演算子オーバーロード
void CumulativeSum::operator=(const CumulativeSum& other) { sum_ = other.sum_; }

void solve() {
    ll N;
    cin >> N;
    ll ALIM = 2010;
    vector<ll> A(N);
    vector<vector<ll>> Mat(ALIM, vector<ll>(N, 0));
    for (int i = 0; i < N; i++) {
        cin >> A[i];
        Mat[A[i]][i] = 1;
    }
    vector<CumulativeSum> css(ALIM);
    for (int a = 0; a < ALIM; a++) {
        css[a] = CumulativeSum(Mat[a]);
    }
    ll ret = 0;
    for (int i = 0; i < N; i++) {
        ll a2 = A[i];
        for (int j = i + 1; j < N; j++) {
            ll a3 = A[j];
            ll k = a2 - a3;
            if (k <= 0) continue;
            ll a1 = a2 - (k + 10);
            if (a1 < 0) continue;
            ll a4 = a3 + (k + 1);
            if (a4 >= ALIM) continue;
            ll tmp1 = css[a1].query(0, i);
            ll tmp2 = css[a4].query(j + 1, N);
            ret += tmp1 * tmp2;
        }
    }
    std::cout << ret << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int T = 1;
    while (T--) {
        solve();
    }
    return 0;
}