#include <iostream>
#include <algorithm>
using namespace std;

int main(){
  int x,y,a,b;
  cin>>x>>y;
  cin>>a>>b;
  int m,d;
  m=min(abs(x),abs(y));
  d=abs(x)+abs(y)-m;
  if(x==y && a==b &&((x>0 && x>a) || (x<0 && x<a))){
    d+=1;
  }
  cout<<d<<endl;
  return 0;
}