题目描述

给出一个由小写字母组成的字符串S，问有多少由小写字母 构成的字条串S',满足 1:|S|'=|S| 2:S'[L..R]是回文串，当且仅当S[L..R]是回文串

输入格式

一个字符串S,长度<=10^6

输出格式

输出答案Mod10^9+7

abba

650
Only words of the form xyyx are palindromically equivalent to abba, where x and y are distinct letters. 
The English alphabet contains 26 letters, consequently there are 26*25=650  such words in total.

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