import java.util.*

fun main(args: Array<String>) {
    val scanner = Scanner(System.`in`)
    val n = scanner.nextInt()
    val b = IntArray(n-1)
    for(i in 0..n-2){
        b[i] = scanner.nextInt()
    }
    var sum = b[0]
    for(i in 0..n-3){
        if(b[i] <= b[i+1]){
            sum += b[i]
        }
        else sum += b[i+1]
    }
    println(sum+b[n-2])
}