def aa(q):
    global mod,x
    return f[q]*g[q]%mod*x%mod
n,k=map(int,input().split());mod=10**9+7
a=list(map(int,input().split()))
x=1
for i in range(1,k+1):
	x*=i;x%=mod
f=[x]*10**6;g=[1]*len(f);x=pow(x,mod-2,mod)
for i in range(1,len(f)):
    f[i]=f[i-1]*(i+k)%mod
    g[i]=g[i-1]*i%mod
g[-1]=pow(g[-1],mod-2,mod)
for i in range(len(f)-1,0,-1):
    g[i-1]=g[i]*i%mod
ans=0
for i in range(n):
    ans+=aa(i)*aa(n-i-1)%mod*a[i]%mod
print(ans%mod)