import java.util.Scanner;

public class Slope {
    public static double calculateSlope(int x0, int y0, int x1, int y1) {
        // avoid dividing by zero
        if(x1 == x0) {
            throw new ArithmeticException("Vertical lines can not have a slope");
        }

        return (double)(y1 - y0) / (double)(x1 - x0);
    }


    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);

        int x0 = in.nextInt();
        int y0 = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();

        try {
            double slope = calculateSlope(x0, y0, x1, y1);
            System.out.println("The slope of the line is " + slope);
        } catch (ArithmeticException e) {
            e.printStackTrace();

            String mesg = e.getMessage();
            System.out.println(mesg);
        }

    }
}