#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

const int N=,INF=1e7;

int n,a[N],pre[N],nxt[N],ans;

struct Node{

    int val,bh;

}tp[N];

bool cmp(Node a,Node b){return a.val<b.val;}

int main()

{

    scanf("%d",&n);

    for(int i=;i<=n;i++)scanf("%d",&a[i]),tp[i].val=a[i],tp[i].bh=i;

    sort(tp+,tp+n+,cmp);

    for(int i=;i<=n;i++)pre[tp[i].bh]=tp[i-].bh,nxt[tp[i].bh]=tp[i+].bh?tp[i+].bh:n+;

    a[n+]=INF;a[]=-INF;

    for(int i=n;i>;i--)

    {

        ans+=min(a[i]-a[pre[i]],a[nxt[i]]-a[i]);

        pre[nxt[i]]=pre[i];nxt[pre[i]]=nxt[i];

    }

    printf("%d",ans+a[]);

    return ;

}