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

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner scan = new Scanner(System.in);
		int x1 = scan.nextInt(), y1 = scan.nextInt();
		int x2 = scan.nextInt(), y2 = scan.nextInt(), z2 = scan.nextInt();
		double D = 1/Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1) + z2 * z2);
		System.out.print(D);
	}
}