Problem C - The archeologist's dilemma
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An archeologist seeking proof of the presence of extraterrestrials in
the Earth's past, stumbles upon a partially destroyed wall containing
strange chains of numbers. The left-hand part of these lines of digits
is always intact, but unfortunately the right-hand one is often lost by
erosion of the stone. However, she notices that all the numbers with all
its digits intact are powers of 2, so that the hypothesis that all of
them are powers of 2 is obvious. To reinforce her belief, she selects a
list of numbers on which it is apparent that the number of legible
digits is strictly smaller than the number of lost ones, and asks you to
find the smallest power of 2 (if any) whose first digits coincide with
those of the list.

Thus you must write a program such that given an integer, it determines
(if it exists) the smallest exponent E such that the first digits of 2^E
coincide with the integer (remember that more than half of the digits
are missing).

Input 
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Input consists of multiple lines, one line per case.  Each line contains
a single positive integer. If there is a power of 2 that corresponds to
this number, it is less or equal to 2147483647, i.e. it fits into a
long. Input is terminated by a line containing 0.

Output 
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For every input N, output the smallest positive
integer E such that the first digits of 2^E are precisely the digits of
N, or, if there is no one, the sentence "no power of 2".

Sample Input 
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1
2
10
0

Output for Sample Input
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7
8
20