#include <iostream>

using namespace std;

int main(){
    int a, b;
    cin >> a >> b;

    if(a > b) {
        int c = a;
        int d = b;

        a = d;
        b = c;
    }
    int brojac = 0;
    for(int i = a; i <= b; i++) {
        if(i % 2 == 0) {
            brojac++;
        }
    }
    cout << brojac << endl;
    return 0;
}