#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>

typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;

ll gcd(ll a, ll b) {
    if (a < b)swap(a, b);
    if (b == 0)return a;
    return gcd(b, a % b);
}
int lcm(int a, int b) {
    return a * b / gcd(a, b);
}

long long mod_exp(long long b, long long e, long long m) {
    if (e > 0 && b == 0) return 0;
    long long ans = 1;
    b %= m;

    while (e > 0) {
        if ((e & 1LL)) ans = (ans * b) % m;
        e = e >> 1LL;
        b = (b * b) % m;
    }

    return ans;
}


int main()
{

    int Q;
    Q = 1;
    //cin >> Q;



    while (Q--) {
        
        string d = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
        int n;
        cin >> n;
        reverse(d.begin(), d.end());
        vector<int>t(d.size() + 5);
        for (int i = 0; i <d.size(); i++)t[i] = d[i] - '0';
        int x = n;
        vector<int>w(d.size() + 5);
        int v = 0;
        
        while (x) {
            int r = x % 10;
            r *= pow(10, v);
            
            for (int i = 0; i <d.size(); i++) {
                w[i] += t[i] * r;
            }
            x /= 10;
            v++;
        }
        for (int i = 0; i < t.size()-2; i++) {
            //if (w[i] <= 9)continue;
            w[i + 1] += w[i] / 10;
            w[i] %= 10;
           
        }
        int T = 0;
        if (n >= 82)T++;
        int cnt = 0;
        for (int i = d.size() + T; i >= 0; i--) {
            cout << w[i];
            if (cnt == T)cout << '.'; cnt++;
            
        }
       

    }
        return 0;
    }