#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    int N;
    cin >> N;
    vector<int> V(N);
    for (int i = 0; i < N; i++) {
        cin >> V[i];
    }
    
    int m = 0;
    int c = 0;
    for (int i = 0; i < N-1; i++) {
        m += max(V[c], V[c+1]);
        if (V[c] < V[c+1]) c += 2;
        else c += 2+1;
    }
    
    cout << m << endl;
    return 0;
}