import java.util.Scanner;

/*
4 0
0 4
-1 -1

 */
public class Accident {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int x1 = scanner.nextInt();
        int y1 = scanner.nextInt();
        int x2 = scanner.nextInt();
        int y2 = scanner.nextInt();
        int x3 = scanner.nextInt();
        int y3 = scanner.nextInt();
        double d1 = calcDist(x1, y1, x2, y2, x3, y3);
        double d2 = calcDist(x2, y2, x3, y3,x1, y1);
        double d3 = calcDist( x3, y3,x1, y1, x2, y2);
        System.out.println(Math.min(d1, Math.min(d2, d3)));
    }

    private static double  calcDist(double x1, double y1, double x2, double y2, double x3, double y3) {
        double midX = (x1+x2)/2;
        double midY = (y1+y2)/2;
        double lenX = Math.abs(midX-x1);
        double lenY = Math.abs(midY-y1);
        double radius = Math.sqrt(lenX*lenX+lenY*lenY);
        return Math.abs(dist(midX, midY, x3, y3) - radius);
    }

    private static double dist(double x1, double y1, double x2, double y2) {
        double lenX = Math.abs(x2 - x1);
        double lenY = Math.abs(y2 - y1);
        double len = Math.sqrt(lenX * lenX + lenY * lenY);
        return len;
    }

}