JaeHyeonKim19

import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int y = sc.nextInt();
		int w = sc.nextInt();
		int h = sc.nextInt();
	 	int min = x;
	 	if(y<min) min = y;
	 	if(w-x<min) min = w-x;
	 	if(h-y<min) min = h-y;
		System.out.print(min);
	}
}