#include <iostream>
#include <vector>

constexpr int INF = 1 << 30;

void solve() {
    int n;
    std::cin >> n;

    std::vector<int> dp(10, -INF);
    dp[0] = 0;
    while (n--) {
        int x;
        std::cin >> x;
        x %= 10;

        auto ndp = dp;
        for (int y = 0; y < 10; ++y) {
            ndp[(x + y) % 10] = std::max(ndp[(x + y) % 10], dp[y] + 1);
        }
        std::swap(dp, ndp);
    }

    std::cout << dp[0] << "\n";
}

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

    solve();

    return 0;
}