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.)

Input

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

Output

Print the answer.

Constraints

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

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

见题面 Input 部分

见题面 Output 部分