#include <bits/stdc++.h> using namespace std; int main(){ int a,b,x,y,minn,s,s1,s2; cin>>a>>b>>x>>y; minn=min(abs(a-x),abs(a-y)); s1=minn; s=abs(b-a); s2=s1+min(abs(b-x),abs(b-y)); cout<<min(s2,s); return 0; }