#include <iostream>
using namespace std;
int main() {
int A1;
int B1;
int A2;
int B2;
int H;
cin>>A1>>B1>>A2>>B2;
if (A1>=A2 && B1>=A1 && B2>=A2);{
H = B1+B2;
cout<<H<<endl;
}
if (A1<=A2 && B1<=B2) {
H=0;
cout<<H<<endl;
}
return 0;
}