#include <iostream>
#include <vector>

using namespace std;

int main() {

    int n;
    cin >> n;

    vector <int> a(n, 0);
    vector <int> b(3, 0);

    for (int i = 0; i < n; i++)
        cin >> a[i];

    long ans = 0;

    for (int i = 0; i < n; i++)
        if (a[i] % 3 == 0) {
            ans += i / 3;
            b[i % 3]++;
        }
        else
            ans += b[i % 3];

    cout << ans;

    return 0;
}