import java.util.Scanner;

public class pp3_5 
{
    public static void main(String[] args) 
{
       double x1,y1,x2,y2;
       double c,a,b;
        
Scanner scan = new Scanner(System.in);
       
System.out.println("Input coordinates x1: ");
        x1 = scan.nextDouble();
        
System.out.println("Input coordinates y1: ");
        y1 = scan.nextDouble();
        
System.out.println("Input coordinates x2: ");
        x2 = scan.nextDouble();
        
System.out.println("Input coordinates y2: ");
        y2 = scan.nextDouble();
        
a = Math.pow((x2-x1),2);
b = Math.pow((y2-y1),2);
c = Math.sqrt(a+b);
        System.out.println("c = "+c);



    }
}