#include <iostream>
#include <string>
#include <iomanip>
#include <vector>
using namespace std;
int ans[200];
int main()
{
	string D = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";


	int n; cin >> n;
	for (int i = D.size()-1; i >= 0; i--) {
		int d = D[i] - '0';

		d *= n;
		int a=d%10, b=d%100/10, c=d%1000/100;
		//cout << a << b << c << endl;
		ans[i+2] += a;
		if (ans[i + 2] >= 10) {
			ans[i + 1] += ans[i + 2]/10;
			ans[i + 2] %= 10;
		}
		ans[i+1] += b;
		if (ans[i + 1] >= 10) {
			ans[i] += ans[i + 1] / 10;
			ans[i + 1] %= 10;
		}
		ans[i] += c;
	}

	bool first = true;
	for (int i = 0; i <= D.size()+1; i++){
		if (i == 0 && ans[i] == 0)continue;
		if (i == 2)cout << '.';
		cout << ans[i];
	}
	cout << endl;
    return 0;
}