Problem Statement

You are given a string $S$ consisting of lowercase English letters.
If a appears in $S$, print the last index at which it appears; otherwise, print $\-1$. (The index starts at $1$.)

Constraints

• $S$ is a string of length between $1$ and $100$ (inclusive) consisting of lowercase English letters.

Input

The input is given from Standard Input in the following format:

$S$

Output

Print the answer.

Sample Input 1

abcdaxayz

Sample Output 1

7

a appears three times in $S$. The last occurrence is at index $7$, so you should print $7$.

Sample Input 2

bcbbbz

Sample Output 2

-1

a does not appear in $S$, so you should print $\-1$.

Sample Input 3

aaaaa

Sample Output 3

5