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