#include<bits/stdc++.h>
int main()
{
    long long n;
    long long storing[150000]={0};
    long long sum;
    scanf("%ld",&n);
    for (int i=1;i<=n;i++)
    {
        scanf("%ld",&storing[i]);
    }
    for (int i=1;i<n;i++)
    {
        if (storing[i]>storing[i+1]) sum+=storing[i];
        else
        {
            sum+=storing[i+1];
        }
    }
    printf("%ld",sum);
}