#include <bits/stdc++.h>
using namespace std;
#define int long long
struct node {
int l, r, m, val = 0, pos = 0;
node *lf = nullptr; node *rg = nullptr;
node (int _l, int _r): l(_l), r(_r), m((_l+_r)/2) {}
pair<int,int> qry(int x, int y) {
if (r < x || l > y) return {0,0};
if (x <= l && r <= y) return {val, pos};
if (!lf) create();
auto tmp1 = lf->qry(x, y);
auto tmp2 = rg->qry(x, y);
if (tmp1.first >= tmp2.first) return tmp1;
else return tmp2;
}
void upd(int p, int v) {
if (l == r) {val = v; pos = l;return;}
if (!lf) create();
if (p <= m) lf->upd(p, v);
else rg->upd(p, v);
if (lf->val >= rg->val) {pos = lf->pos; val = lf->val;}
else {pos = rg->pos; val = rg->val;}
}
void create() {
if (l != r) {
lf = new node(l, m);
rg = new node(m+1, r);
}
}
}*root;
//build cartesian tree because i have to :(
vector<vector<int>> adj(100005);
int cost[100005];
void build(int s, int e, int p) {
if (e < s) return;
int x = root->qry(s, e).second;
if (p != -1) adj[p].push_back(x);
build(s, x-1, x);
build(x+1, e, x);
}
int ans;
void dfs(int n, int p) {
for (auto i:adj[n]) {
dfs(i, n);
ans += cost[i]+cost[n];
}
}
signed main() {
int n; cin >> n;
for (int i = 0; i < n; i++) cin >> cost[i];
root = new node(0, n);
for (int i= 0; i < n; i++) root->upd(i, cost[i]);
build(0, n-1, -1);
ans = 0;
dfs(root->qry(0, n-1).second, -1);
cout << ans;
}
