#include<bits/stdc++.h>
using namespace std;
int a,b,x,y;
int main()
{
    cin>>a>>b>>x>>y;
    if(min(abs(y-a)+abs(x-b),abs(y-b)+abs(x-a))<b-a)
    {
        cout<<min(abs(y-a)+abs(x-b),abs(y-b)+abs(x-a));
    }
    else
    {
        cout<<b-a;
    }
    return 0;
}