#include "iostream"
using namespace std;
const int BORDER = 10;

int N;
int up;
char box[200] = { "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991" };
int down[200];

int main() {
	cin >> N;
	for (int i = 0; box[i]!= NULL ; i++) {
		down[i] = box[i] - '0';
	}
	up = down[0] * N / BORDER;
	down[0] = (down[0] * N) % BORDER;

	for (int i = 1; i < 200; i++) {
		down[i - 1] += down[i] * N / BORDER;
		down[i] = (down[i] * N)%BORDER;
	}
	for (int i = 199; i >= 1; i--) {
		if (down[i] >= BORDER) {
			down[i - 1] += down[i] / 10;
			down[i] %= 10;
		}
	}
	up += down[0] / 10;
	down[0] %= 10;
	cout << up << ".";
	for (int i = 0; i < 200; i++) {
		cout << down[i];
	}
	cout << "\n";
	return 0;
}