1010 Radix (25)（25 分）
Given a pair of positive integers, for example, 6 and 110, can this
equation 6 = 110 be true? The answer is "yes", if 6 is a decimal number
and 110 is a binary number.
Now for any pair of positive integers N1 and N2, your task is to find
the radix of one number while that of the other is given.
Input Specification:
Each input file contains one test case. Each case occupies a line which
contains 4 positive integers:\
N1 N2 tag radix\
Here N1 and N2 each has no more than 10 digits. A digit is less than its
radix and is chosen from the set {0-9, a-z} where 0-9 represent the
decimal numbers 0-9, and a-z represent the decimal numbers 10-35. The
last number "radix" is the radix of N1 if "tag" is 1, or of N2 if "tag"
is 2.
Output Specification:
For each test case, print in one line the radix of the other number so
that the equation N1 = N2 is true. If the equation is impossible, print
"Impossible". If the solution is not unique, output the smallest
possible radix.
Sample Input 1:
6 110 1 10
Sample Output 1:
2
Sample Input 2:
1 ab 1 2
Sample Output 2:
Impossible
