CF360C Levko and Strings

Levko loves strings of length $ n $ , consisting of lowercase English letters, very much. He has one such string $ s $ . For each string $ t $ of length $ n $ , Levko defines its beauty relative to $ s $ as the number of pairs of indexes $ i $ , $ j $ $ (1

The first line contains two integers $ n $ and $ k $ ( $ 1

Print a single number — the answer to the problem modulo $ 1000000007 $ $ (10^{9}+7) $ .