nCr={}
def cmb(n,r):
    if r==0 or r==n: return 1
    if r==1: return n
    if (n,r) in nCr: return nCr[(n,r)]
    nCr[(n,r)] = cmb(n-1,r) + cmb(n-1,r-1)
    return nCr[(n,r)]
N=int(input())
a=[*map(lambda args:args[1]*cmb(N-1,args[0]),enumerate([*map(int,input().split())]))]
print(int(sum(a)%1000000007))