#include <iostream>
using namespace std;

int main(){
int a,b;
cin>>a>>b;
cout<<(b-b%2)/2-(a+a%2)/2+1;
}

#include <iostream>
using namespace std;

int main(){
int a,b;
cin>>a>>b;
cout<<((b-b%2)-(a+a%2))/2+1;
}