#include <iostream>
using namespace std;

int main() {
    int N; cin >> N;
    int ans; ans = 0;
  	int s = 1e5 + 1;
    for (int i = 0; i < N-1; i++) {
        int a; cin >> a;
      	ans += min(s, a);
      	s = a;
    }
  	cout << ans + s << endl;
}