N = int(input())
L = list(map(int,input().split()))

ans = 0
mod = 10**9 + 7
now = L[0]
for i in range(N-1):
    ans += now * 2 * pow(3,N-2-i,mod)
    ans %= mod
    now *= L[i+1]
    now %= mod
#print(ans)
print((ans + now)%mod)