e-olymp
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

Print only small Latin letters a from the given string. If the letter a is not in the string, then print - 1.

Time limit 1 second
Memory limit 128 MiB
Input example #1
abrakadabra
Output example #1
aaaaa
Input example #2
qwertyuiop sdfghjkl
Output example #2
-1
Author Matviychuk Sergiy Volodymyrovych
Source "ABC programming"