import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final long D = sc.nextLong();
		final long D8 = D * 8;
		
		final long upper_ans = D + (D8 / 100);
		final long lower_ans = D8 % 100;
		
		System.out.println(upper_ans + "." + String.format("%02d", lower_ans));
	}

}