List <int> Calc()
{
var N = G()[0];
var a = G();
var r = new int[N];
for (var i = 0; i < N; i++)
{
r[--a[i]] = i;
}
var par = new[] { new RMQ(a, 0), new RMQ(a, 1) };
var q = new PQ();
var d = new Dictionary <int, P>();
Action <P> add = p => { if (p.r - p.l > 1)
{
var z = par[p.l & 1].Min(p); d[z] = p; q.Enqueue(z);
}
};
add(new P(0, N));
var L = new List <int>();
while (q.N > 0)
{
int x = q.Dequeue(), i = r[x];
var p = d[x];
int f = p.l & 1, y = par[1 - f].Min(i + 1, p.r), j = r[y];
L.Add(x + 1);
L.Add(y + 1);
add(new P(p.l, i));
add(new P(i + 1, j));
add(new P(j + 1, p.r));
}
return(L);
}
int[] DijkstraFrom(int from)
{
var d = new int[V];
for (var i = 0; i < V; i++)
{
d[i] = Inf;
}
var queue = new PQ();
d[from] = 0;
queue.Enqueue(new P(from, 0));
while (queue.Count > 0)
{
var p = queue.Dequeue();
int u = p.First, tmp = d[u] + (dead.Contains(u) ? 1 : 0);
if (d[u] < p.Second)
{
continue;
}
var k = es[u].Count;
for (var i = 0; i < k; i++)
{
int v = es[u][i];
if (d[v] > tmp)
{
queue.Enqueue(new P(v, d[v] = tmp));
}
}
}
return(d);
}