Arthur and Alexander are number busters. Today they've got a competition. Arthur took a group of four integers a, b, w, x (0 ≤ b w, 0 x w) and Alexander took integer с . Arthur and Alexander use distinct approaches to number bustings. Alexander is just a regular guy. Each second, he subtracts one from his number. In other words, he performs the assignment: c = c - 1. Arthur is a sophisticated guy. Each second Arthur performs a complex operation, described as follows: if b ≥ x , perform the assignment b = b - x , if b x , then perform two consecutive assignments a = a - 1; b = w - (x - b). You've got numbers a, b, w, x, c . Determine when Alexander gets ahead of Arthur if both guys start performing the operations at the same time. Assume that Alexander got ahead of Arthur if c ≤ a .

输入描述:

The first line contains integers a, b, w, x, c(1 ≤ a ≤ 2·109, 1 ≤ w ≤ 1000, 0 ≤ b w, 0 x w, 1 ≤ c ≤ 2·109).

输出描述:

Print a single integer — the minimum time in seconds Alexander needs to get ahead of Arthur. You can prove that the described situation always occurs within the problem's limits.