Question 8 : Longest Prefix and Suffix

A non empty string containing only alphabets.
Print the longest prefix from the input string which is same as suffix.
Prefix and Suffix should not be overlapped.
Print -1 if there is no prefix exist which is also the suffix without overlap.
Note : Do case sensitive comparison.

Constraints

1 <= Length of String <= 1000

Input Format :
You will be given string of only alphabets in one line.

Output Format : Print longest prefix according to given rules above in one line.
If there is no prefix which is also suffix without overlap then print -1.

Test Case 1

Input :
xxAbcxxAbcxx

Output : xx

Explanation 1

xx in the prefix and xx in the suffix and this is longest one in the input string.
hence output will be xx.

Test Case 2

Input :
Racecar

Output : -1

Explanation 2

There is no any prefix which is also in suffix.
Note : Comparison should be case sensitive so according to case sensitive rule R and r are two different alphabets in the input string.
hence output will be -1.