Given any integer 0 ≤ n ≤ 10000 not divisible
by 2 or 5, some multiple of n is a number which
in decimal notation is a sequence of 1’s. How
many digits are in the smallest such a multiple
of n?
Input
A ?le of integers at one integer per line.
Output
Each output line gives the smallest integer x > 0
such that p =
∑x−1
i=0 1×10i = a×b, where a is the
corresponding input integer, and b is an integer
greater than zero.
Sample Input
3
7
9901
Sample Output
3
6
12
原文：http://www.cnblogs.com/guochen/p/5377715.html