#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define rep3(i, l, n) for (int i = l; i < n; ++i)
#define chmax(a, b) a = (a >= b ? a : b)
#define chmin(a, b) a = (a <= b ? a : b)
#define out(a) cout << a << endl
#define outa(a, n) rep(_, n) cout << a[_] << " "; cout << endl
#define SZ(v) (int)v.size()
#define inf (int)(1e9+7)
#define abs(x) (x >= 0 ? x : -(x))
#define ceil(a, b) a / b + !!(a % b)
#define FIX(a) fixed << setprecision(a)

int main() {
    string str = "0.1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
    int n;
    cin >> n;
    int c = 0;
    string t;
    for (int i = SZ(str) - 1; i >= 0; --i) {
        if (i == 1) { t += '.'; continue; }
        int tmp = str[i] - '0';
        // out(tmp);
        tmp *= n;
        tmp += c;
        c = tmp / 10;
        tmp %= 10;
        t += tmp + '0';
    }
    if (c) t += c + '0';
    reverse(all(t));
    out(t);
}