import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.util.StringTokenizer; public class Main { static BufferedReader in; static PrintWriter out; static StringTokenizer tok; void solve() throws IOException { int[] d = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991".chars().map(c -> c - '0').toArray(); int n = ni(); int[] ans = new int[192]; for (int i = 189; i >= 0; i--) { ans[i + 2] += d[i] * n; if (ans[i + 2] >= 10) { ans[i + 1] += ans[i + 2] / 10; ans[i + 2] %= 10; } } int x = ans[0] * 10 + ans[1]; out.print(x + "."); for (int i = 2; i < 192; i++) { out.print(ans[i]); } } String ns() throws IOException { while (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine(), " "); } return tok.nextToken(); } int ni() throws IOException { return Integer.parseInt(ns()); } long nl() throws IOException { return Long.parseLong(ns()); } double nd() throws IOException { return Double.parseDouble(ns()); } String[] nsa(int n) throws IOException { String[] res = new String[n]; for (int i = 0; i < n; i++) { res[i] = ns(); } return res; } int[] nia(int n) throws IOException { int[] res = new int[n]; for (int i = 0; i < n; i++) { res[i] = ni(); } return res; } long[] nla(int n) throws IOException { long[] res = new long[n]; for (int i = 0; i < n; i++) { res[i] = nl(); } return res; } public static void main(String[] args) throws IOException { in = new BufferedReader(new InputStreamReader(System.in)); out = new PrintWriter(System.out); tok = new StringTokenizer(""); Main main = new Main(); main.solve(); out.close(); } }