A bitstring, whose length is one less than a prime, might be
magic.
1001 is one such string. In order to see the
magic in the string let us append a non-bit
x to it,
regard the new
thingy as a cyclic string, and make this
square matrix of bits
| each bit |
1001 |
| every 2nd bit |
0110 |
| every 3rd bit |
0110 |
| every 4th bit |
1001 |
This matrix has the same number of rows as the length of the original
bitstring. The
m-th row of the matrix has every
m-th
bit of the original string starting with the
m-th bit. Because
the enlarged
thingy has prime length, the appended
x
never gets used.
If each row of the matrix is either the original bitstring or its complement,
the original bitstring is
magic.
For each prime number from the input
produce one line of output containing the lexicographically smallest,
non-constant magic bitstring of length p-1, if such a
string exists, otherwise output Impossible.