You are given a set of n elements indexed from 1 to n. The weight of i-th element is wi. The weight of some subset of a given set is denoted as . The weight of some partition R of a given set into k subsets is (recall that a partition of a given set is a set of its subsets such that every element of the given set belongs to exactly one subset in partition).
Calculate the sum of weights of all partitions of a given set into exactly k non-empty subsets, and print it modulo 109 + 7. Two partitions are considered different iff there exist two elements x and y such that they belong to the same set in one of the partitions, and to different sets in another partition.
The first line contains two integers n and k (1 ≤ k ≤ n ≤ 2·105) — the number of elements and the number of subsets in each partition, respectively.
The second line contains n integers wi (1 ≤ wi ≤ 109)— weights of elements of the set.
Print one integer — the sum of weights of all partitions of a given set into k non-empty subsets, taken modulo 109 + 7.
2 3 2 3
1 2 3 4 5
Possible partitions in the first sample:
Possible partitions in the second sample: