package backjoon;

// https://www.acmicpc.net/problem/1085

// 직사강형에서의 탈출

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

public class _1085 {

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

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

//sol memory 11500 runtime 80

String[] nums = br.readLine().split(" ");

int x = Integer.parseInt(nums[0]);

int y = Integer.parseInt(nums[1]);

int w = Integer.parseInt(nums[2]);

int h = Integer.parseInt(nums[3]);

int min = x;

min = Math.min(min, y);

min = Math.min(min, w-x);

min = Math.min(min, h-y);

System.out.println(min);

}

}

/*

input

6 2 10 3

output

1

*/