import sys
from operator import itemgetter
from collections import defaultdict, deque
import heapq
import bisect

stdin=sys.stdin
sys.setrecursionlimit(10 ** 8)

ip=lambda: int(sp())
fp=lambda: float(sp())
lp=lambda:list(map(int,stdin.readline().split()))
sp=lambda:stdin.readline().rstrip()
Yp=lambda:print('Yes')
Np=lambda:print('No')
inf = 1 << 60
eps = 1e-9
sortkey = itemgetter(0)
mod = 10 ** 9+ 7

###############################################################
N = ip()
A = lp()
ans = 0
## a1 +- a2...

now = 1

for i in range(N - 1):
    now *= A[i]
    ans += now * 2 * pow(3, N - 1 - (i + 1), mod)
    ans %= mod
ans += now * A[-1]
ans %= mod
print(ans)