import java.io.PrintWriter
import java.util.*
import kotlin.math.*

// region ModInt
class ModInt(x: Long) {
    companion object {
        const val MOD = 1000000007L
        //const val MOD = 998244353L
    }

    constructor(y: Int) : this(y.toLong())

    val x = (x % MOD + MOD) % MOD

    operator fun plus(other: ModInt): ModInt {
        return ModInt(x + other.x)
    }

    operator fun minus(other: ModInt): ModInt {
        return ModInt(x - other.x)
    }

    operator fun times(other: ModInt): ModInt {
        return ModInt(x * other.x)
    }

    operator fun div(other: ModInt): ModInt {
        return this * other.inv()
    }

    fun pow(exp: Long): ModInt {
        if (exp == 0L) return ModInt(1L)
        var a = pow(exp shr 1)
        a *= a
        if (exp and 1L == 0L) return a
        return this * a
    }

    fun inv(): ModInt {
        return this.pow(MOD - 2)
    }

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (javaClass != other?.javaClass) return false

        other as ModInt

        if (x != other.x) return false

        return true
    }

    override fun hashCode(): Int {
        return x.hashCode()
    }

    override fun toString(): String {
        return "$x"
    }
}

fun Long.toModInt(): ModInt {
    return ModInt(this)
}

fun Int.toModInt(): ModInt {
    return ModInt(this)
}

const val fac_size = 600000
var fac_initialized = false
val arr_fac = Array(fac_size) { ModInt(1) }
val arr_invfac = Array(fac_size) { ModInt(1) }

fun facInitialize() {
    for (i in 1 until fac_size) {
        arr_fac[i] = arr_fac[i - 1] * ModInt(i)
    }
    arr_invfac[fac_size - 1] = arr_fac[fac_size - 1].inv()
    for (i in fac_size - 2 downTo 1) {
        arr_invfac[i] = arr_invfac[i + 1] * ModInt(i + 1)
    }
    fac_initialized = true
}

fun fac(n: Int): ModInt {
    if (!fac_initialized) facInitialize()
    return arr_fac[n]
}

fun fac(n: Long): ModInt {
    return fac(n.toInt())
}

fun invfac(n: Int): ModInt {
    if (!fac_initialized) facInitialize()
    return arr_invfac[n]
}

fun invfac(n: Long): ModInt {
    return invfac(n.toInt())
}

fun comb(n: Long, k: Long): ModInt {
    return if (k in 0..n) {
        fac(n) * invfac(k) * invfac(n - k)
    } else {
        ModInt(0)
    }
}

fun comb2(n: Long, k: Long): ModInt {
    var numer = ModInt(1)
    var denom = ModInt(1)
    for (i in 0 until k) {
        numer *= ModInt(n - i)
        denom *= ModInt(k - i)
    }
    return numer / denom
}
// endregion

val pow2 = Array(35) { 1L }

fun PrintWriter.solve() {
    for (i in 0 until pow2.count() - 1) {
        pow2[i + 1] = pow2[i] * 2
    }
    val n = nextInt()
    val b = Array(n) { nextLong() }
    var prev = 0L
    var streak = 0L
    var ans = ModInt(1)
    for (i in 0 until n) {
        if (b[i] == -1L) streak++
        else {
            var c01 = 0L
            var c11 = 0L
            for (j in 0 until 32) {
                when ((prev.shr(j) % 2) to (b[i].shr(j) % 2)) {
                    0L to 1L -> {
                        c01++
                    }
                    1L to 1L -> {
                        c11++
                    }
                    1L to 0L -> {
                        println(0)
                        return
                    }
                }
            }
            ans *= calc(streak + 1, c01, c11)
            prev = b[i]
            streak = 0L
        }
    }
    println(ans)
}

fun calc(a: Long, b: Long, c: Long): ModInt {
    var ret = ModInt(0)
    for (i in 0..b) {
        val v = comb(b, i) * ModInt(pow2[(b + c - i).toInt()] - 1).pow(a)
        if (i % 2 == 0L) ret += v
        else ret -= v
    }
    return ret
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve()
    writer.flush()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()!!
fun nextDouble() = next().toDouble()
// endregion