import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] b = arrayInt(sc, n - 1);
		sc.close();
		int[] a = new int[n];
		int sum = 0;
		a[0] = b[0];
		for (int i = 0; i < n - 1; i++) {
			if (a[i] > b[i]) {
				a[i] = b[i];
			}
			a[i + 1] = b[i];
			sum += a[i];
		}
		sum += a[n - 1];
		System.out.println(sum);
	}

	public static long modFactorial(long n, long mod) {
		long ans = 1;
		for (int i = 1; i <= n; i++) {
			ans *= i;
			ans %= mod;
		}
		return ans;
	}

	public static int arrayMax(int[] array) {
		int ans = Integer.MIN_VALUE;
		for (int i = 0; i < array.length; i++) {
			if (array[i] > ans)
				ans = array[i];
		}
		return ans;
	}

	public static int[] arrayInt(Scanner sc, int n) {
		int[] array = new int[n];
		for (int i = 0; i < n; i++) {
			array[i] = sc.nextInt();
		}
		return array;
	}

	public static long[] arrayLong(Scanner sc, int n) {
		long[] array = new long[n];
		for (int i = 0; i < n; i++) {
			array[i] = sc.nextLong();
		}
		return array;
	}

	public static double[] arrayDouble(Scanner sc, int n) {
		double[] array = new double[n];
		for (int i = 0; i < n; i++) {
			array[i] = sc.nextDouble();
		}
		return array;
	}
}

class Combination {
	static final int MOD = 1000000007;
	long[] fac;
	long[] finv;
	long[] inv;

	public Combination(int size) {
		fac = new long[size];
		finv = new long[size];
		inv = new long[size];
		fac[0] = 1;
		fac[1] = 1;
		finv[0] = 1;
		finv[1] = 1;
		inv[1] = 1;
		for (int i = 2; i < size; i++) {
			fac[i] = fac[i - 1] * i % MOD;
			inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
			finv[i] = finv[i - 1] * inv[i] % MOD;
		}
	}

	public long getComb(int n, int k) {
		if (n < k || n < 0 || k < 0) {
			return 0;
		}
		return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz