#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n,lft=0,rit=0,ans=0,i=0,big;
    int arr[100001];
    cin >> n;
    for (int i=0;i<n;i++)
        cin >> arr[i];
    while(lft<n)
    {
        big = 0;
        while(rit<n&&arr[rit]>arr[rit+1])
        {
            int mx = max(arr[rit],arr[rit+1]);
            big = max(big,mx);
            rit++;
        }
        rit++;
        ans+=big;
        lft=rit;
    }
        cout << ans << endl;
}