import java.math.BigInteger;
import java.util.Scanner;
import java.util.Vector;

public class Main {
	public static void main(String[] args) {
		@SuppressWarnings("resource")
		Scanner scanner = new Scanner(System.in);

		int N = scanner.nextInt();

		int[] scannerArrayB = new int[N - 1];

		long ans = 0;

		for (int index = 0; index < N - 1; index++) {
			scannerArrayB[index] = scanner.nextInt();
		}

		ans = scannerArrayB[0];

		for(int i = 0; i < N-2; i++) {
			ans += Math.min(scannerArrayB[i], scannerArrayB[i+1]);
		}

		ans += scannerArrayB[N-2];


//		for(int index = 0; index < N - 1; index++) {
//			ans += scannerArrayB[index];
//		}

		log(ans);
	}

	private static void dfs(int[] treeArray,int parrent, int children) {
		Vector<Vector> aa = new Vector<>();
		Vector<Integer> bb = new Vector<>();
		bb.add(1);
		aa.add(bb);
	}


	/**
	 * バブルソートの交換数を算出
	 * ※転倒数
	 * @param array
	 * @return
	 */
	private static long countSwapBabbleSort(int[] array, int N) {
		long ans = 0;
		int[] binary = new int[N + 1];

		for (int index = 0; index < array.length; index++) {
			ans = ans + (index - sum(binary, array[index]));
			add(binary, array[index], 1);
		}
		return ans;
	}

    //add value at idx on bit O(logN)
	private static void add(int[] bit,int idx,int value) {
        for(int i=idx;i<bit.length;i=i+(i&-i)) {
        	bit[i] += value;
        }
    }

    //return sum [1,idx] O(logN)
	private static long sum(int[] bit,int idx) {
        long ret = 0;
        for(int i=idx;i>0;i-=(i&-i)) {
        	ret += bit[i];
        }
        return ret;
    }

	private static void log(String str) {
		System.out.println(str);
	}

	private static void log(int str) {
		System.out.println(str);
	}

	private static void log(long str) {
		System.out.println(str);
	}

	private static void log(double str) {
		System.out.println(str);
	}

	private static void log(BigInteger str) {
		System.out.println(str);
	}

}


/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