Palindromic Equivalence

内存限制：128 MiB 时间限制：10 Sec

提交提交记录讨论

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

一个字符串S,长度<=10^6

输出答案Mod10^9+7

样例输入


			abba

样例输出


			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.