76 - ZOJ 7th Anniversary Contest - A
It was said that when testing the first computer designed by von Neumann, people gave the following problem to both the legendary professor and the new computer: If the 4th digit of 2^n is 7, what is the smallest n? The machine and von Neumann began computing at the same moment, and von Neumann gave the answer first.
Now you are challenged with a similar but more complicated problem: If the K-th digit of M^n is 7, what is the smallest n?
Each case is given in a line with 2 numbers: K and M (< 1,000).
For each test case, please output in a line the smallest n.
You can assume:
3 2 4 2 4 3
15 21 11
Author: CHEN, Yue
Source: ZOJ 7th Anniversary Contest