#include<iostream> //输入函数库 #include<iomanip> #include<cmath> //数学函数库 #include<cstdio> #include<ctime> #include<cstring> #include<cstdlib> #include<string> #include<stdlib.h> #include<sys/time.h> #include<queue> //队列 #include<stack> //栈 using namespace std; int main(){ int x,y,a,b; cin>>x>>y>>a>>b; if(abs(b-y)>=abs(a-x)){ cout<<abs(b-y); } else{ cout<<abs(a-x); } return 0; }