#line 1 "main.cpp"
#include <iostream>
#include <algorithm>
#include <numeric>
#include <vector>
#include <string>

using namespace std;
using lint = long long;

void solve() {
    lint n;
    cin >> n;

    lint ones = 0, twos = 0;
    for (int i = n; i--;) {
        int x;
        cin >> x;

        if (x == 1) {
            ++ones;
        } else if (x == 2) {
            ++twos;
        }
    }

    cout << n * (n - 1) / 2 +
                ones * (ones - 1) / 2 * 1 +
                ones * twos * 2
         << "\n";
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();

    return 0;
}