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Competitions

# 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"