#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,r1,r2; cin>>a>>b>>c>>d; r1=abs(a-c),r2=abs(b-d); if(r1>r2){ cout<<r1; } else{ cout<<r2; } return 0; }