import sys
input = sys.stdin.buffer.readline

def main():
    N = int(input()); MOD = pow(10,9) + 7
    A = list(map(int,input().split()))
    fac = 2*pow(3,N-2,MOD)
    inv3 = pow(3,MOD-2,MOD)
    ans = 0
    a = 1
    for i in range(N-1):
        a = a*A[i]%MOD
        #print(a,fac)
        ans += a*fac
        ans %= MOD
        #facの更新
        fac = fac*inv3%MOD
    #最後はfac無し
    ans += a*A[N-1]%MOD
    print(ans%MOD)

if __name__ == '__main__':
    main()