#include <bits/stdc++.h>
using
namespace
std;
int
main()
{
int
a,b,c,d,e,f;
cin>>a>>b>>c>>d;
e=
abs
(a-c);
f=
abs
(b-d);
cout<<max(e,f);
return
0;
}
#include <bits/stdc++.h>
using
namespace
std;
int
main()
{
int
a,b,c,d,e,f;
cin>>a>>b>>c>>d;
e=
abs
(a-c);
f=
abs
(b-d);
cout<<max(e,f);
return
0;
}