Multigram

Pero is a passionate lover of riddles. The newest type of riddles he has come across requires the solver to check whether the given word is a multigram.

A multigram is a word that consists of concatenating two or
more words that are all mutually anagrams. The first of these
words is called the root of the multigram. For instance, the
word `bbabab` is a multigram with the
root `bba` because it consists of
anagrams `bba` and `bab`.

Help Pero solve the riddle by determining whether his word is a multigram and determining its root in case it is. If there are multiple possible roots of the multigram, output the shortest.

Note: Two words are mutually anagrams if one of them can be obtained from the other by changing the letter order.

The first and only line of input contains a word of length at most $100\, 000$ lowercase English characters.

If the given word is not a multigram, output `-1`. Otherwise, output the shortest root of the
given word in one line.

Sample Input 1 | Sample Output 1 |
---|---|

aaaa |
a |

Sample Input 2 | Sample Output 2 |
---|---|

ab |
-1 |

Sample Input 3 | Sample Output 3 |
---|---|

bbabab |
bba |