# include<iostream> #include<cstdio> using namespace std; int main(){ int a,b,c,d; int n=0,z=0; scanf("%d%d%d%d",&a,&b,&c,&d); if(a>b){ n=a-c; }else{ n=b-d; } if(c>d){ z=c-a; }else{ z=d-b; } if(n>z){ cout<<n; }else{ cout<<z; } return 0; }