import sys

sys.setrecursionlimit(10 ** 6)
def II(): return int(sys.stdin.readline())

def main():
    md = 10 ** 9 + 7
    n = II()
    ee = [II() for _ in range(n)]
    ans = 0
    for sj in range(2):
        for sk in range(2):
            dp = [[[0] * 2 for _ in range(2)] for _ in range(n + 1)]
            dp[0][sj][sk] = 1
            for i, e in enumerate(ee):
                for j in range(2):
                    for k in range(2):
                        pre = dp[i][j][k] % md
                        if pre == 0: continue
                        if (j, k, e) == (0, 1, 0): continue
                        if (j, k, e) == (0, 1, 1):
                            dp[i + 1][k][0] += pre
                            dp[i + 1][k][1] += pre
                        elif k == e:
                            dp[i + 1][k][0] += pre
                        else:
                            dp[i + 1][k][1] += pre
            ans += dp[n][sj][sk]
    print(ans % md)

main()