#include <iostream>
#include <cstdio>
using namespace std;

int n, s, b[105];
int main() {
	int i;
	cin >> n;
	for(i=1; i<n; i++) cin >> b[i];
	b[0] = b[n] = 1e9;
	for(i=1; i<=n; i++) s += min(b[i], b[i-1]);
	cout << s;
	return 0;
}