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

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		double xa, ya, za, xb, yb, zb;
		Scanner in = new Scanner(System.in);
		
		xa = in.nextDouble();
		ya = in.nextDouble();
		za = in.nextDouble();
		xb = in.nextDouble();
		yb = in.nextDouble();
		zb = in.nextDouble();
		
		double AB = Math.sqrt((xb-xa)*(xb-xa)+(yb-ya)*(yb-ya)+(zb-za)*(zb-za));
		
		System.out.println(AB);
	}
}