

import java.io.*;
class Main {
public static void main(String[] args) throws Exception {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String[] input = br.readLine().split(" ");
int[] nums = new int[4];
for (int i = 0; i < input.length; i++) {
nums[i] = Integer.parseInt(input[i]);
}
int[] distances = new int[4];
distances[0] = Math.abs(nums[0] - nums[2]) + Math.abs(nums[1] - nums[3]);
distances[1] = Math.abs(nums[0] - nums[3]) + Math.abs(nums[1] - nums[2]);
distances[2] = Math.abs(nums[0] - nums[2]) + Math.abs(nums[1] - nums[3]);
distances[3] = Math.abs(nums[0] - nums[3]) + Math.abs(nums[1] - nums[2]);
int maxDistance = distances[0];
for (int i = 1; i < distances.length; i++) {
if (distances[i] > maxDistance) {
maxDistance = distances[i];
}
}
System.out.println(maxDistance);
}
}