def gcd(x, y):
    while y != 0:
        (x, y) = (y, x % y)
    return x
l,r,p,q=map( int , raw_input().split() )
t=1
ans=0
while p**t <= r :
	z=t+1
	tavanp=p ** t
	tavanp1=p ** z
	tavanq=q ** t
	lcm=tavanp*tavanq/(gcd(tavanp,tavanq))
	lcm3=(tavanp1*tavanq)/(gcd(tavanp1,tavanq))
	plus=(r/tavanp) - ( (l-1)/tavanp )
	minus=(r/lcm) - ( (l-1)/lcm )
	minus1=(r/tavanp1) - ( (l-1)/tavanp1 )
	plus1=(r/lcm3) - ( (l-1)/lcm3 )
	ans=ans+plus-minus-minus1+plus1
	t=t+1;
print(ans);
 
 

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