import math

def gcd(a, b):
    while b:
        a %= b
        a, b = b, a
    return a

l, r, p, q = map(int, raw_input().strip().split(' '))
ol, oR, op, oq = l, r, p, q
if p == q:
    print 0
    exit()
gcdpq = gcd(p, q)
l = int(math.ceil(float(l)/gcdpq))
r = int(float(r)/gcdpq)
p /= gcdpq
q /= gcdpq
if p == 1:
    total = None
    if q % op != 0:
        total = (oR / op - (ol - 1) / op) - (oR / oq - (ol - 1) / oq) + (oR / (op * oq) - (ol - 1) / (op * oq))
    else:
        total = (oR / op - (ol - 1) / op)
    print total
    exit()
if q == 1:
    print 0
    exit()

maxppower = int(math.log(r, p))
maxqpower = int(math.log(r, q))
total = 0
doubleremoved = 0
for power in xrange(maxppower, 0, -1):
    poweredp = p ** power
    poweredq = q ** power
    total = r / poweredp - (l - 1) / poweredp - ((r / (poweredp * poweredq) - (l - 1) / (poweredp * poweredq)) - doubleremoved)
    doubleremoved = r / (poweredp * q ** (power - 1)) - (l - 1) / (poweredp * q ** (power - 1)) - (r / (poweredp * poweredq) - (l - 1) / (poweredp * poweredq))

print total