# include<iostream> # include<cmath> using namespace std; int main(){ int x1,y1,x2,y2,x,y;//x是x1和x2的距离，y是y1和y2的距离 scanf("%d%d%d%d",&x1,&y1,&x2,&y2); x=abs(x1-x2); y=abs(y1-y2); if(x>y) cout<<x<<endl; else cout<<y<<endl; return 0; }