mod=10**9+7
n=int(input())
A=list(map(int,input().split()))

ans=0
cur=1
for i in range(n-1):
    cur*=A[i]
    cur%=mod

    now=(pow(3,n-2-i,mod)*2)*cur
    ans+=now
    ans%=mod
print((ans+cur*A[n-1])%mod)