import sys
from collections import defaultdict, deque, Counter
import math

# import copy
from bisect import bisect_left, bisect_right
import heapq

# sys.setrecursionlimit(1000000)

# input aliases
input = sys.stdin.readline

getS = lambda: input().strip()
getN = lambda: int(input())
getList = lambda: list(map(int, input().split()))
getZList = lambda: [int(x) - 1 for x in input().split()]

INF = 10 ** 20
MOD = 10 ** 9 + 7
divide = lambda x: pow(x, MOD - 2, MOD)


def nck(n, k, kaijyo):
    return (npk(n, k, kaijyo) * divide(kaijyo[k])) % MOD


def npk(n, k, kaijyo):
    if k == 0 or k == n:
        return n % MOD
    return (kaijyo[n] * divide(kaijyo[n - k])) % MOD

def kaijyo(n):
    ret = [1]
    for i in range(1, n + 1):
        ret.append((ret[-1] * i)% MOD)
    return ret

def kaijyo_kai(n, k):
    ret = [1]
    for i in range(1, n + 1):
        ret.append((ret[-1] * (k+i))% MOD)
    return ret


def solve():
    n, k = getList()
    nums = getList()

    ans = 0
    kai = kaijyo(n+1)
    kaikai = kaijyo_kai(n, k)
    # print(kai)
    # print(kaikai)
    for i, num in enumerate(nums):
        tmp = num * kaikai[i] * divide(kai[i]) * kaikai[n-i-1] * divide(kai[n-i-1])
        ans += tmp

        ans %= MOD

    print(ans)



def main():
    n = getN()
    for _ in range(n):
        solve()


if __name__ == "__main__":
    # main()
    solve()