import java.util.Scanner;
public class Main1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
double x1 = in.nextDouble();
double y1 = in.nextDouble();
double x2 = in.nextDouble();
double y2 = in.nextDouble();
Point p1 = new Point(x1, y1);
Point p2 = new Point(x2, y2);
Line line = new Line(p1, p2);
System.out.printf("%.2f\n", line.slope());
in.close();
}
}
class Point{
static double x;
static double y;
public Point(double x,double y){
this.x=x;
this.y=y;
}
public double getX(){
return x;
}
public double getY(){
return y;
}
public static void setX(double x) {
Point.x = x;
}
public static void setY(double y) {
Point.y = y;
}
}
class Line
{
private Point p1;
private Point p2;
public Line(Point p1,Point p2)
{
this.p1=p1;
this.p2=p2;
}
public double slope()
{
double s=(p2.getY()-p1.getY())/(p2.getX()-p1.getX());
return s;
}
}
