#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,y1,x2,y2; cin>>x1>>y1>>x2>>y2; int h1,h2; h1=abs(x2-x1); h2=abs(y2-y1); if(h1>h2){ cout<<h1<<endl; } else{ cout<<h2<<endl; } return 0; }