SPOJ in Gyumri

   There is a trouble in Numberland, prime number p is jealous of another prime number q. She thinks that there are more integer numbers between a and b, inclusively, that are divisible by greater power of q than that of p. Help p to get rid of her feelings.

   Let α(n, x) be maximal k such that n is divisible by xk . Let us say that a number n is p-dominating over q if α(n, p) > α(n, q). Find out for how many numbers between a and b, inclusive are p-dominating over q.

Input

   The first line of the input file contains a, b, p and q (1 ≤ a ≤ b ≤ 10¹⁸; 2 ≤ p, q ≤ 10⁹; p ƒ= q; p and q are prime).

Output

   Output one number — how many numbers n between a and b, inclusive, are p-dominating over q.

Example