//

//  main.c

//  practice

//

//  Created by Chen on 2018/6/24.

//  Copyright © 2018年 Chen. All rights reserved.

//

#include <stdio.h>

#include <math.h>

int main(int argc, const char * argv[]) {

    int a,b;

    while (scanf("%d%d",&a,&b)!=EOF) {

        int sum=(b-a)/2 +(!(a%2)||!(b%2));

        printf("%d\n",sum);

    }

    return 0;

}