312

//312
#include <cstdio>
#include <algorithm>
using namespace std;

int main(void) {
    FILE* fin = fopen("input.txt", "r");
    FILE* fout = fopen("output.txt", "w");

    int n, p = 0, last_elem, current_elem;
    fscanf(fin, "%d", &n);
    fscanf(fin, "%d", &last_elem);
    p = 2 + 2 * last_elem;
    for (int i = 1; i < n; ++ i) {
        fscanf(fin, "%d", &current_elem);
        p += (2 + 2 * current_elem) - 2 * min(last_elem, current_elem);
        last_elem = current_elem;
    }
    fclose(fin);
    fprintf(fout, "%d\n", p);
    fclose(fout);
    return 0;
}