import java.util.*;
class Main
{
    public static void main(String[] args)
    {
        new Main().run();
    }
    
    
    
    void run()
    {
    	Scanner sc=new Scanner(System.in);
    	long A=sc.nextLong();
    	long B=sc.nextLong();
    	long C=sc.nextLong();
    	long D=sc.nextLong();
    	
    	assert(-1e9<=A&&A<=1e9);
    	assert(-1e9<=B&&B<=1e9);
    	assert(-1e9<=C&&C<=1e9);
    	assert(-1e9<=D&&D<=1e9);
    	
    	C-=A;
    	D-=B;
    	C=Math.abs(C);
    	D=Math.abs(D);
    	assert(!(C==0&&D==0));
    	if (C==0||D==0) {
    		System.out.println(1);
    	} else if (C+D<=3) {
    		System.out.println(1);
    	} else {
    		System.out.println(2);
    	}
    }
    
    
    void tr(Object...objects) {System.out.println(Arrays.deepToString(objects));}
}