import sys
input=lambda: sys.stdin.readline().rstrip()
n,k=map(int,input().split())
A=[int(i) for i in input().split()]
mod=10**9+7
n_max=2*(10**5+1)
F,FI=[0]*(n_max+1),[0]*(n_max+1)
F[0],FI[0]=1,1
for i in range(n_max):
  F[i+1]=(F[i]*(i+1))%mod
FI[n_max-1]=pow(F[n_max-1],mod-2,mod)
for i in reversed(range(n_max-1)):
  FI[i]=(FI[i+1]*(i+1))%mod
def comb(x,y):
  return (F[x]*FI[x-y]*FI[y])%mod
def hom(x,y):
  return comb(x+y-1,y)

H=[0]*(n+1)
H[0]=1
for i in range(n):
  H[i+1]=(H[i]*(k+i+1)*pow(i+1,mod-2,mod))%mod
ans=0
for i,a in enumerate(A):
  ans=(ans+a*(H[i]*H[n-i-1]))%mod
print(ans)