#include<bits/stdc++.h>
using namespace std;
int a[1000010];
int main()
{
    int n;
    long long ans = 0;
    scanf("%d", &n);
    for(int i = 1; i <= n; ++i) scanf("%d", &a[i]);
    for(int i = 2; i <= n; ++i) ans += max(a[i], a[i - 1]);
    printf("%lld\n", ans);
    return 0;
}