import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class ccc10j5 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int startR = sc.nextInt()-1;
		int startC = sc.nextInt()-1;
		int endR = sc.nextInt()-1;
		int endC = sc.nextInt()-1;

		int[][] step = new int[8][8];
		//fill with Integer.MAX_VALUE
		for (int r=0; r<8; r++) {
			Arrays.fill(step[r], Integer.MAX_VALUE);
		}

		LinkedList<Integer> rQ = new LinkedList<Integer>();
		LinkedList<Integer> cQ = new LinkedList<Integer>();

		//initialize beginning location
		step[startR][startC] = 0;
		rQ.add(startR);
		cQ.add(startC);

		while(!rQ.isEmpty()) {
			int r = rQ.poll();   //read current position's row
			int c = cQ.poll();

			//1. r-2   c+1
			if (r-2>=0 && c+1<8  //check the boudary
					&& step[r-2][c+1]>step[r][c]+1) {
				step[r-2][c+1] = step[r][c]+1;
				rQ.add(r-2);
				cQ.add(c+1);
			}
			//2. r-1   c+2
			if (r-1>=0 && c+2<8  //check the boudary
					&& step[r-1][c+2]>step[r][c]+1) {
				step[r-1][c+2] = step[r][c]+1;
				rQ.add(r-1);
				cQ.add(c+2);
			}
			//3. r+1   c+2
			//4. r+2   c+1
			//5. r+2   c-1
			//6. r+1   c-2
			//7  r-1   c-2
			//8  r-2   c-1
		}

		System.out.println(step[endR][endC]);

	}

}