#include <iostream>
#include <string>

int main() {
    uint32_t n;
    std::cin >> n;
    uint64_t s = 1;
    for (uint32_t i = 0; i < n; ++i) {
        uint64_t p;
        std::cin >> p;
        s *= p;
    }
    std::string t = std::to_string(s);
    while (t.size() != 1) {
        uint64_t u = 0;
        for (auto c : t) {
            u += c - '0';
        }
        s = u;
        t = std::to_string(s);
    }
    std::cout << s << std::endl;
}