# include<bit/stdc++.> using namespace std; int main(){ int a,b,c,d; cin>>a>>b>>c>>d; if(a>c){ int x=a-c; }else{ int x=c-a; } if(b>d){ int y=b-d; }else{ int y=d-b; } if(x>y){ cout<<x; }else{ cout<<y; } return 0; }