import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Back_1085 {

    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());

        int x = Integer.parseInt(st.nextToken());
        int y = Integer.parseInt(st.nextToken());
        int w = Integer.parseInt(st.nextToken());
        int h = Integer.parseInt(st.nextToken());

        int xMin = Math.min(x, w - x);
        int yMin = Math.min(y, h - y);

        System.out.println(Math.min(xMin,yMin));
        br.close();
    }
}