import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileWriter; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.util.ArrayList; import java.util.Comparator; import java.util.HashSet; import java.util.List; public class Main { public static void main(String[] args) throws NumberFormatException, IOException { ContestScanner in = new ContestScanner(); int x = in.nextInt(); int y = in.nextInt(); int x2 = in.nextInt(); int y2 = in.nextInt(); System.out.println(Math.abs(x-x2) + Math.abs(y-y2) + ((x == 0 && x2 == 0 && y2 < y) || (y == 0 && y2 == 0 && x2 < x)?2:0)); } } class Node{ int id; HashSet edge = new HashSet(); public Node(int id) { this.id = id; } public void createEdge(Node node) { edge.add(node); } } class MyComp implements Comparator { final int idx; public MyComp(int idx){ this.idx = idx; } public int compare(int[] a, int[] b) { return a[idx] - b[idx]; } } class Reverse implements Comparator { public int compare(Integer arg0, Integer arg1) { return arg1 - arg0; } } class ContestWriter { private PrintWriter out; public ContestWriter(String filename) throws IOException { out = new PrintWriter(new BufferedWriter(new FileWriter(filename))); } public ContestWriter() throws IOException { out = new PrintWriter(System.out); } public void println(String str) { out.println(str); } public void println(Object obj) { out.println(obj); } public void print(String str) { out.print(str); } public void print(Object obj) { out.print(obj); } public void close() { out.close(); } } class ContestScanner { private BufferedReader reader; private String[] line; private int idx; public ContestScanner() throws FileNotFoundException { reader = new BufferedReader(new InputStreamReader(System.in)); } public ContestScanner(String filename) throws FileNotFoundException { reader = new BufferedReader(new InputStreamReader(new FileInputStream( filename))); } public String nextToken() throws IOException { if (line == null || line.length <= idx) { line = reader.readLine().trim().split(" "); idx = 0; } return line[idx++]; } public String readLine() throws IOException{ return reader.readLine(); } public long nextLong() throws IOException, NumberFormatException { return Long.parseLong(nextToken()); } public int nextInt() throws NumberFormatException, IOException { return (int) nextLong(); } public double nextDouble() throws NumberFormatException, IOException { return Double.parseDouble(nextToken()); } }