package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	if n == 1 {
		Println(0)
		return
	}
	a := make([]int, n)
	for i := range a {
		Scan(&a[i])
	}
	a[n-1] = a[n-2]
	ans,cnt := 0, 0
	for i := n-1; i >= 0; i-- {
		cnt++
		if i < n-1 && a[i] == 1 {
			ans += cnt
		}
		if i > 0 && a[i-1]==a[i] {
			cnt = 0
		}
	}
	Println(ans)
}