#include <bits/stdc++.h>
using namespace std;

int main() {
    int n; cin >> n;
    vector<int> dp(10, -1);
    dp[0] = 0;
    for(int _ = 0; _ < n; ++_) {
        int a; cin >> a; a %= 10;
        vector<int> np(dp);
        for(int i = 0; i < 10; ++i) {
            if(dp[i] == -1) continue;
            int j = (i + a) % 10;
            np[j] = max(np[j], dp[i] + 1);
        }
        dp = np;
    }
    cout << dp[0] << '\n';
    return 0;
}