#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,s,d,f,b,c; cin>>a>>s>>d>>f; b=d-a,c=f-s; if(b<0){ b=b*(-1); }else{ b=b+0; } if(c<0){ c=c*-1; }else{ c=c*0+c; } if(c<b){ cout<<b;} else{ cout<<c; } return 0; }