
ZOJ Problem Set  1222
The expression N!, read as "N factorial," denotes the product of the first N positive integers, where N is nonnegative. So, for example, N N! For this problem, you are to write a program that can compute the last nonzero digit of the factorial for N. For example, if your program is asked to compute the last nonzero digit of 5!, your program should produce "2" because 5! = 120, and 2 is the last nonzero digit of 120.
Input to the program is a series of nonnegative integers, each on its own line with no other letters, digits or spaces. For each integer N, you should read the value and compute the last nonzero digit of N!.
For each integer input, the program should print exactly one line of output containing the single last nonzero digit of N!.
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1 Source: South Central USA 1997 