#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
const int N = 1e3 + 10;

int n;
int cnt[N];

main()
{
    cin >> n;
    for (int i = 1; i <= n; ++i)
    {
        int x;
        cin >> x;
        cnt[x]++;
    }

    ll ans = 0;

    for (int i = 0; i <= 1000; ++i)
    {
        ans += cnt[i] * (cnt[i] - 1) / 2;
    }
    ans += cnt[0] * (n - cnt[0]);
    cout << ans;

    return 0;
}