import java.util.Scanner;

public class Main {

    void solve() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] B = new int[N - 1];
        for (int i = 0; i < N - 1; i++) {
            B[i] = sc.nextInt();
        }
        int[] A = new int[N];
        A[0] = B[0];
        A[N - 1] = B[N - 2];

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

        int ans = 0;
        for (int i = 0; i < N; i++) {
            ans += A[i];
        }
        System.out.print(ans);
    }

    // Main
    public static void main(String[] args) {
        new Main().solve();
    }
}
/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