#13304: ___c
10555088@mail.hpsh.tp.edu.tw
(3.141592653589793238462)
#include <stdio.h>
int main(){
int a,b,i,sum=0;
scanf("%d%d",&a,&b);
b-=b%2;a+=a%2;
printf("%d\n",(b-a)/2+1);
return 0;
}