Problem Description

Given a string \( S \) consisting of lowercase characters.

The value of a string is defined as the number of distinct non-empty subsequences of the string, where a subsequence can be the string itself.

Calculate the sum of the values of all subsequences of \( S \). The answer should be taken modulo \( 10^9 + 7 \).

Input Format

The first line contains a string \( S \) consisting of lowercase characters.

Output Format

Output a single line containing the answer.

Sample Input and Output

Sample Input #1

ab

Sample Output #1

5

Sample Input #2

sapnap

Sample Output #2

593

Sample Input #3

abcbdabcbabcd

Sample Output #3

938773

Sample Input #4

tobeornottobethatisthequestion

Sample Output #4

769276982

Notes

Data Size and Constraints

This problem uses batched testing.

• Subtask 1 (5 pts): \( |S| \le 11 \).
• Subtask 2 (10 pts): \( |S| \le 22 \).
• Subtask 3 (20 pts): \( |S| \le 100 \) and \( S \) consists only of characters a and b.
• Subtask 4 (30 pts): \( |S| \le 5000 \).
• Subtask 5 (35 pts): No additional constraints.

For \( 100\% \) of the data, \( 1 \le |S| \le 10^6 \), and \( S \) consists only of lowercase characters.

见题面 Input 部分

见题面 Output 部分