#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;


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

    string s = "0.1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";

    int n;
    cin>>n;
    reverse(s.begin(),s.end());
    s.pop_back();
    s.pop_back();
    int m = s.size();
    vector<int> a(m,0);
    for(int i = 0;i<m;i++) a[i] = 0;
    for(int i = 0;i<m;i++){
        int now = s[i] - '0';
        now *= n;
        now += a[i];
        a[i] = 0;
        int ni = i;
        while(now){
            int use = now % 10;
            if(ni>=a.size()){
                a.push_back(0);
            }
            a[ni] += use;
            ni++;
            now /= 10;
        }
    }

    string t = "";
    bool fn = false;
    for(int i = 0;i<a.size();i++){
        if(i==m) {
            t += ".";
            fn = true;
        }

        t += '0' + a[i];
    }
    if(!fn) t += ".0";
    
    reverse(t.begin(),t.end());
    cout<<t<<endl;

}