Problems
Only one letter
Only one letter
Print only small Latin letters a found in the given string.
Input data
One line consisting only of small Latin letters and spaces.
Output data
Print only small Latin letters a from the given string. If the letter a is not in the string, then print -1.
Examples
Input example #1
abrakadabra
Output example #1
aaaaa
Input example #2
qwertyuiop sdfghjkl
Output example #2
-1