import math

mod = 1_000_000_007


def popcnt(n):
    c = (n & 0x5555555555555555) + ((n >> 1) & 0x5555555555555555)
    c = (c & 0x3333333333333333) + ((c >> 2) & 0x3333333333333333)
    c = (c & 0x0F0F0F0F0F0F0F0F) + ((c >> 4) & 0x0F0F0F0F0F0F0F0F)
    c = (c & 0x00FF00FF00FF00FF) + ((c >> 8) & 0x00FF00FF00FF00FF)
    c = (c & 0x0000FFFF0000FFFF) + ((c >> 16) & 0x0000FFFF0000FFFF)
    c = (c & 0x00000000FFFFFFFF) + ((c >> 32) & 0x00000000FFFFFFFF)
    return c


def COM(n, r):
    if n < r:
        return 0
    return math.factorial(n) // math.factorial(r) // math.factorial(n - r) % mod


n = int(input())
b = list(map(int, input().split()))
base, cont, res = 0, 0, 1
for v in b:
    if v == -1:
        cont += 1
    else:
        for i in range(30):
            if base >> i & 1 and v >> i & 1 == 0:
                print(0)
                exit()

        a = popcnt(base)
        b = popcnt(v)
        x = b - a
        tmp = 0
        for i in range(0, x + 1):
            tmp += COM(x, i) * pow((pow(2, b - i, mod) - 1), cont + 1, mod) * (-1 if i % 2 else 1)
            tmp %= mod
        res *= tmp

        cont, base = 0, v

print(res)