#a121

from math import sqrt

while True:
    try:
        a,b=map(int,input().split())
        a,b=min(a,b),max(a,b)
        number=[i for i in range(a,b+1)]

        for candidate in range(2,int(sqrt(b))+1):
            trial=candidate*candidate
            while trial<=b:
                if trial in number:
                    number.remove(trial)
                trial+=candidate
        print(len(number))
    except:
        break