#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define vec vector<ll>
#define sortv(a); sort(a.begin(), a.end());
#define rev(a); reverse(a.begin(), a.end());
#define FOR(i,a,b) for (ll i = (ll)(a); i < (b); i++)
#define ROF(i,a,b) for (ll i = (ll)(b)-1; i >= (a); i--)

ll MOD = 1000000007;
ll INF = 1LL << 60;

int main() {
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	
	int n;
	cin >> n;
	vec a(n), b(n-1);
	FOR(i,0,n-1) {
		cin>>b[i];
	}
	a[n-1]=INF;
	for(int i=n-2;i>=0;i--) {
		a[i+1]=min(a[i+1],b[i]);
		a[i]=b[i];
	}
	ll out=0;
	FOR(i,0,n) {
		out+=a[i];
	}
	cout<<out;
}