#include <iostream>
#include <algorithm>
#include <string>

std::string s = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";

void solve() {
    std::reverse(s.begin(), s.end());
    int n;
    std::cin >> n;

    std::string ans = "";
    int up = 0;
    for (char c : s) {
        int x = c - '0';
        x *= n;
        x += up;

        up = x / 10;
        x %= 10;
        ans.push_back(x + '0');
    }

    std::reverse(ans.begin(), ans.end());
    std::cout << up << "." << ans << std::endl;
}

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

    solve();

    return 0;
}