CF288B Polo the Penguin and Houses

Little penguin Polo loves his home village. The village has $ n $ houses, indexed by integers from 1 to $ n $ . Each house has a plaque containing an integer, the $ i $ -th house has a plaque containing integer $ p_{i} $ ( $ 1

The single line contains two space-separated integers $ n $ and $ k $ ( $ 1

In a single line print a single integer — the answer to the problem modulo $ 1000000007 $ $ (10^{9}+7) $ .