import java.util.*

fun main(args: Array<String>) {
	val scanner = Scanner(System.`in`)
	val n = scanner.nextInt()
	var bBef = scanner.nextInt()
	var ans = bBef;
	for (i in 2..n-1){
		val bi = scanner.nextInt()
		ans += Math.min(bBef, bi)
		bBef = bi
	}
	ans += bBef
	println(ans)
}