include<bits/stdc++.h>

using namespace std; int main() {

int x1,y1,x2,y2,a,b;
cin>>x1>>y1>>x2>>y2;
if(x1>x2) a=x1-x2;
else a=x2-x1;
if(y1>y2) b=y1-y2;
else b=y2-y1;
cout<<a+b;
return 0;

}