#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

int main(){
  int n;
  cin >> n;
  string D = "0.1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
  int b[200]; // b少数部分、[0] -> 最上位桁の数
  FOR (i,0,200) {
    b[i] = 0;
  }
  for (int i = 2; i < D.length(); i++) {
    b[i-2] = D[i] - '0';
  }
  for (int i = 199; i >= 0; i--) {
    b[i] = b[i] * n;
  }
  int kuriagari = 0;
  for (int i = 199; i >= 0; i--) {
    b[i] += kuriagari;
    kuriagari = b[i] / 10;
    b[i] = b[i] % 10;
  }
  printf("%d.",kuriagari);
  FOR(i,0,200) {
    printf("%d",b[i]);
  }
  cout << endl;
  return 0;
}