n = int(input())
A = list(map(int,input().split()))
mod = 10**9+7
three = 1
dp = [A[0],0]
ans = 0
for i,a in enumerate(A[1:],1):
    ndp = [0,0]
    ans += dp[0]*pow(3,n-1-i,mod)*2%mod
    ans -= dp[1]*pow(3,n-1-i,mod)*2%mod
    ans %= mod
    ndp[0] += dp[0]*a
    ndp[0] += three*a
    ndp[0] %= mod
    ndp[1] += dp[1]*a
    ndp[1] += three*a
    ndp[1] %= mod
    dp = ndp
    three *= 3
    three %= mod

print((ans+dp[0]-dp[1])%mod)