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

fun PrintWriter.solve() {
    val n = nextInt()
    val a = Array(n) { nextInt() }
    var ans = 0L
    fun isIncreasing(): Boolean {
        for (i in 1 until n) {
            if (a[i] < a[i - 1]) return false
        }
        return true
    }
    fun helper() {
        if (a.all { it == 0 }) {
            ans++
            return
        }
        for (i in 0 until n) {
            if (a[i] >= 2) {
                a[i] -= 2
                if (isIncreasing()) helper()
                a[i] += 2
            }
        }
        for (i in 1 until n) {
            if (a[i] >= 1 && a[i - 1] >= 1 && a[i] == a[i - 1]) {
                a[i]--
                a[i - 1]--
                if (isIncreasing()) helper()
                a[i]++
                a[i - 1]++
            }
        }
    }
    helper()
    println(ans)
}

fun main() {
    Thread(null, {
        val writer = PrintWriter(System.out, false)
        writer.solve()
        writer.flush()
    }, "solve", abs(1L.shl(26)))
        .apply { setUncaughtExceptionHandler { _, e -> e.printStackTrace(); kotlin.system.exitProcess(1) } }
        .apply { start() }.join()
}

// 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