import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.Scanner;

class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		double x1, y1, z1, x, y, S;
		Scanner in = new Scanner(System.in);
		x = in.nextInt();
		y = in.nextInt();
		x1 = in.nextInt();
		y1 = in.nextInt();
		z1 = in.nextInt();
		S = Math.sqrt((x1 - x)*(x1 - x) + (y1-y)*(y1-y) + z1*z1);
		System.out.printf("%.3f", 1/S);
	}
}