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 fun PrintWriter.solve() { 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(1L.shl((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