#include "bits/stdc++.h"
using namespace std;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define rrep(i,n) for( int i = n; i >= 0; i-- )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define RREP(i,s,t) for( int i = s; i >= t; i-- )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000


int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
	string D = "0.1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
	vector<int> A;
	A.push_back(0);
	rep(i, D.size() - 2) {
		A.push_back(D[i + 2] - '0');
	}
	int N; 
	cin >> N;
	for (int i = (int)A.size() - 1; i >= 0; i--) {
		A[i] *= N;
	}
	for (int i = (int)A.size() - 1; i > 0; i--) {
		while (A[i] > 9) {
			A[i] -= 10;
			A[i - 1]++;
		}
	}
	cout << A[0] << '.';
	rep(i, (int)A.size() - 1) cout << A[i + 1];
	cout << endl;

    return 0;
}