import java.util.*;

public class Main {
    static final long MOD = 10000000000L;
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	String BASE = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
    	String[] arr = new String[19];
    	for (int i = 0; i < 19; i++) {
    	    arr[i] = BASE.substring(i * 10, (i + 1) * 10);
    	}
    	int n = sc.nextInt();
    	String[] ans = new String[19];
    	long next = 0;
    	for (int i = 18; i >= 0; i--) {
    	    long value = Long.parseLong(arr[i]) * n + next;
    	    ans[i] = String.format("%010d", value % MOD);
    	    next = value / MOD;
    	}
    	StringBuilder sb = new StringBuilder();
    	sb.append(next).append(".");
    	for (String s : ans) {
    	    sb.append(s);
    	}
    	System.out.println(sb);
	}
}