package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var n int64
	if _, err := fmt.Fscan(in, &n); err != nil {
		return
	}

	var sumH, sumMinAdj int64
	var prev, h int64
	for i := int64(1); i <= n; i++ {
		fmt.Fscan(in, &h)
		sumH += h
		if i > 1 {
			if prev < h {
				sumMinAdj += prev
			} else {
				sumMinAdj += h
			}
		}
		prev = h
	}
	hn := prev
	total := 2*sumH - 2*sumMinAdj - hn + (2*n - 1)
	fmt.Fprintln(out, total)
}