#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int a,b,c,d,n,x; n=0; x=0; cin>>a>>b>>c>>d; if(abs(a-c)>abs(d-b)) { cout<<abs(a-c)<<endl; } else cout<<abs(b-d)<<endl; return 0; }