#include <iostream>
using namespace std;

int main()
{
	int l, N;
	cin >> N;

	int B[N-1];
	for(int i=0; i<N-1 && cin>>l; i++) B[i] = l;

	int sum = B[0];
	for(int i=1; i<N-1; i++) sum += (B[i-1] < B[i]) ? B[i-1] : B[i];
	sum += B[N-2];

	cout << sum; 
}