import java.io.BufferedReader
import java.io.InputStream
import java.io.InputStreamReader
import java.io.PrintWriter
import java.util.*

fun PrintWriter.solve(sc: FastScanner) {
    val n = sc.nextInt()
    val a = Array(n) { sc.nextInt() }
    val M = 1000000007
    if (a.contains(0)) {
        println(-1)
    } else if (a.any { it >= 4 }) {
        println(M)
    } else {
        var v = 1L
        for (i in 0 until n) {
            if (a[i] == 2) v *= 4
            else if (a[i] == 3) v *= 729
            if (v > M) {
                println(M)
                return
            }
        }
        println(M % v)
    }
}

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

class FastScanner(s: InputStream) {
    private var st = StringTokenizer("")
    private val br = BufferedReader(InputStreamReader(s))

    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()
    fun ready() = br.ready()
}