#include <iostream>
#include <vector>
#include <unordered_map>
#include <algorithm>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    using ll = int64_t;
    unordered_map<int, ll> count;
    for (int i = 0; i < n; ++i) {
        int a;
        cin >> a;
        count[a]++;
    }

    vector<int> stick;
    for (auto it : count) {
        stick.push_back(it.first);
    }
    sort(stick.begin(), stick.end());
    int m = (int)stick.size();

    ll res = 0;
    // Case 1: Two single-stick sides
    // Goal: Count pair of pair (a1, b1) (a2, b2) s.t. a1+b1=a2+b2=stick[i]
    for (int i = 1; i < m; ++i) {
        if (count[stick[i]] < 2) continue;
        ll cur = 0;
        ll ans = 0;
        for (int j = i-1; j >= 0; --j) {
            if (2 * stick[j] < stick[i]) break;
            if (2 * stick[j] == stick[i]) {
                ll c = count[stick[j]];
                ans += c * (c - 1LL) * (c - 2LL) * (c - 3LL) / 24LL;
                ans += c * (c - 1LL) / 2LL * cur;
                cur += c * (c - 1LL) / 2LL;
            }
            else {
                ll a = count[stick[i] - stick[j]];
                ll b = count[stick[j]];
                ans += a * (a - 1LL) * b * (b - 1LL) / 4LL;
                ans += a * b * cur;
                cur += a * b;
            }
        }
        ll t = count[stick[i]];
        res += t * (t - 1LL) / 2LL * ans;
    }

    // Case 2: Three single-stick sides
    // Goal: Count number of triplets (a, b, c) s.t. a+b+c=stick[i]
    unordered_map<int, ll> two;
    for (int i = 0; i < m; ++i) {
        int k = 2 * stick[i];
        ll c = count[stick[i]];
        two[k] += c * (c - 1LL) / 2LL;
        for (int j = i+1; j < m; ++j) {
            int k = stick[i] + stick[j];
            if (k > stick[m-1]) break;
            two[k] += count[stick[i]] * count[stick[j]];
        }
    }

    for (int i = 1; i < m; ++i) {
        if (count[stick[i]] < 3) continue;
        ll ans = 0;
        for (int j = i-1; j >= 0; --j) {
            int k = stick[i] - stick[j];
            ll a = two[k];
            if (k > stick[j]) {
                a -= count[k - stick[j]];
                if (2 * stick[j] == k) ++a;
            }
            ans += count[stick[j]] * a;
        }
        ll c = count[stick[i]];
        ans = ans / 3LL;
        ans = ans * c * (c - 1LL) * (c - 2LL) / 6LL;
        res += ans;
    }

    cout << res << '\n';
    return 0;
}