include [HTML_REMOVED]
using namespace std;
//#include [HTML_REMOVED]
int main() {
int a, b,c,d;
cin>>a>>b>>c>>d;
if(b<a){int t=a;a=b;b=t;}
if(d<c){int t=c;c=d;d=t;}
//cout<<a<<b<<c<<d;
int direct_distence=b-a;
if(c>=b||d<=a)cout<<direct_distence;
else if(c>=a&&d<=b)cout<<c-a+b-d;
else if(c>=a&&c<=b&&d>b){
int distence=c-a+d-b;
if(distence<direct_distence)cout<<distence;
else cout<<direct_distence;
}
else if(c[HTML_REMOVED]=a){
int distence=a-c+b-d;
if(distence<direct_distence)cout<<distence;
else cout<<direct_distence;
// 3 4 5 6 7 8 9 10
//2 3 4 5 6 7 8
}
}