#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 x1,x2,y1,y2; cin>>x1>>y1>>x2>>y2; if(abs(x1-x2)>abs(y1-y2)){ cout<<abs(x1-x2)<<endl; } else{ cout<<abs(y1-y2)<<endl; } return 0; }