#include<bits/stdc++.h> using namespace std; typedef long long ll; const int N=1e6+5; int n,a[N]; ll ans; int main(){ scanf("%d",&n); for(int i=1;i<=n;i++){ scanf("%d",&a[i]); if(i==1) continue; ans+=max(a[i],a[i-1]); } printf("%lld\n",ans); return 0; }