#include<bits/stdc++.h>
using namespace std;
int x,y,a,b;
int main(){
	scanf("%d%d%d",&a,&b,&x,&y);
	int ans=0;
	ans=abs(a-b);
	ans=min(ans,abs(x-a)+abs(y-b));
	ans=min(ans,abs(x-b)+abs(y-a));
	printf("%d",ans);
	return 0;
}

40pts