SIZE=2*10**5+1; MOD=10**9+7 #998244353 #ここを変更する

inv = [0]*SIZE  # inv[j] = j^{-1} mod MOD
fac = [0]*SIZE  # fac[j] = j! mod MOD
finv = [0]*SIZE # finv[j] = (j!)^{-1} mod MOD
fac[0] = fac[1] = 1
finv[0] = finv[1] = 1
for i in range(2,SIZE):
    fac[i] = fac[i-1]*i%MOD
finv[-1] = pow(fac[-1],MOD-2,MOD)
for i in range(SIZE-1,0,-1):
    finv[i-1] = finv[i]*i%MOD
    inv[i] = finv[i]*fac[i-1]%MOD

n,k = map(int,input().split())
*a, = map(int,input().split())

perm = [1]*SIZE
for i in range(1,SIZE):
    perm[i] = perm[i-1]*(k+i)%MOD

def chofuku(i):
    return perm[i-1]*finv[i-1]%MOD

ans = 0
for i,ai in enumerate(a):
    ans += ai*chofuku(i+1)%MOD*chofuku(n-i)%MOD
print(ans%MOD)