#include <stdio.h>

void main(void){
    int a,b,c,d;
    scanf("%d %d %d %d",&a,&b,&c,&d);
    int x = c-a;
    if(x < 0){
        x *= -1;
    }
    int y = d-b;
    if(y < 0){
        y *= -1;
    }
    if(x == 0 || y == 0 || x+y <= 3){
        printf("1");
    }else{
        printf("2");
    }
}