#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
import bisect
import heapq


def input():
    return sys.stdin.readline()[:-1]


# sys.setrecursionlimit(1000000)

# _INPUT = """3
# 1 2 3
# """
# sys.stdin = io.StringIO(_INPUT)

INF = 10**10

MOD = 1000000007

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

ans = 0
s = 1
for i in range(N):
    s = (s * A[i]) % MOD
    if i < N-1:
        ans = (ans + s * 2 * pow(3, N-2-i, MOD)) % MOD
    else:
        ans = (ans + s) % MOD
print(ans)