mod = 10**9+7
D = 32


class Combination:
    """
    SIZEが10**6程度以下の二項係数を何回も呼び出したいときに使う
    使い方:
    comb = Combination(SIZE, MOD)
    comb(10, 3) => 120
    """

    def __init__(self, N, MOD=10 ** 9 + 7):
        self.MOD = MOD
        self.__make_factorial_list(N)

    def __call__(self, n, k):
        if k < 0 or k > n:
            return 0
        res = self.fact[n] * self.inv[k] % self.MOD
        res = res * self.inv[n - k] % self.MOD
        return res

    def nPk(self, n, k):
        if k < 0 or k > n:
            return 0
        return self.fact[n] * self.inv[n - k] % self.MOD

    def nHk(self, n, k):
        if k == 0:
            return 1
        return self.__call__(n + k - 1, k)

    def __make_factorial_list(self, N):
        self.fact = [1] * (N + 1)
        self.inv = [1] * (N + 1)
        MOD = self.MOD
        for i in range(1, N + 1):
            self.fact[i] = (self.fact[i - 1] * i) % MOD
        self.inv[N] = pow(self.fact[N], MOD - 2, MOD)
        for i in range(N, 0, -1):
            self.inv[i - 1] = (self.inv[i] * i) % MOD
        return


def main():
    N = int(input())
    B = list(map(int, input().split()))
    comb = Combination(N+1000, mod)
    pow2 = [1] * (N + 1)
    for i in range(1, N + 1):
        pow2[i] = pow2[i-1] * 2 % mod

    def ok(A, B):
        for i in range(D):
            a = (A >> i) & 1
            b = (B >> i) & 1
            if a == 1 and b == 0:
                return 0
        return 1

    def enum(A, B, step):
        res = 0
        for zero in range(step + 1):
            cnt = 1
            for i in range(D):
                a = (A >> i) & 1
                b = (B >> i) & 1
                if a == b == 1:
                    cnt *= pow2[step - zero]
                    cnt %= mod
                if a == 0 and b == 1:
                    cnt *= pow2[step - zero] - 1
                    cnt %= mod
            if zero % 2 == 1:
                cnt = -cnt
                # cnt = mod - cnt
            res = (res + cnt * comb(step, zero)) % mod
        return res

    ans = 1
    i = 0
    a = 0
    step = 0
    while i < N:
        b = B[i]
        i += 1
        if b == -1:
            step += 1
            continue
        if not ok(a, b):
            return 0
        ans *= enum(a, b, step + 1)
        ans %= mod
        a = b
        step = 0
    return ans


print(main())