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

fun PrintWriter.solve() {
    val n = nextInt()
    val a = IntArray(n) { nextInt() }
    val b = IntArray(n) { i -> if (i % 2 == 0) a[i] else 1 - a[i] }
    val c = IntArray(n) { 0 }
    var streak = 1
    var prev = -1
    for (i in n - 1 downTo 0) {
        if (i == n - 1) {
            streak = 0
            prev = b[i]
        } else if (b[i] != prev) {
            prev = b[i]
            streak = 1
        } else {
            streak++
        }
        c[i] = streak
    }
    var ans = 0L
    for (i in 0 until n - 1) {
        if (a[i] == 1) ans += c[i]
    }
    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