#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <unordered_map>
#include <map>
#include <set>
#include <iomanip>

int main() {
    std::string s;
    std::cin >> s;
    int k;
    std::cin >> k;
    int cnt = s.size();
    long double kek = 0, kek_last = 1;
    for (size_t i = 0; i < k; i++) {
        kek = kek * (cnt - 2) / cnt + (1 - kek) * 2 / (cnt * (cnt - 1));
        kek_last = kek_last * (cnt - 2) / cnt + (1 - kek_last) * 2 / (cnt * (cnt - 1));
    }
    int sum = 0;
    for (char c : s) {
        sum += c - '0';
    }
    long double res = 0;
    for (size_t i = 0; i < s.size() - 1; i++) {
        if (s[i] == '5' || ((s[i] - '0') % 2 == 0 && sum % 3 == 0)) {
            res += kek;
        }
    }
    if (s.back() == '5' || ((s.back() - '0') % 2 == 0 && sum % 3 == 0)) {
        res += kek_last;
    }
    std::cout << std::fixed << std::setprecision(10);
    std::cout << res;
}