This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vt vector
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int) (x).size()
#pragma GCC optimize ("O3")
#pragma GCC optimize ("O2")
#define F first
#define S second
//#define endl '\n'
//#define int long long
#define inbuf_len 1 << 16
#define outbuf_len 1 << 16
using namespace std;
const int const_lg = 20;
struct node
{
    char val;
    int h;
    vt<int> children, parent;
    node() { }
    node(char val_, int parent_, int h_)
    {
        val = val_, h = h_;
        parent.pb(parent_);
    }
};
vt<node> trie;
vt<int> commands;
void Init()
{
    trie.pb({'#', 0, -1});
    commands.pb(0);
}
void TypeLetter(char L)
{
    int i = *commands.rbegin();
    trie[i].children.pb(sz(trie));
    trie.pb({L, i, trie[i].h + 1});
    for(int i = 1, v = sz(trie) - 1; trie[i - 1].val != '#'; i++)
    {
        //cout << v << " " << i << " " << trie[trie[v].parent[i - 1]].parent.size() << endl;
        trie[v].parent.pb(trie[trie[v].parent[i - 1]].parent[i - 1]);
        //cout << "ok" << endl;
    }
    commands.pb(sz(trie) - 1);
}
void UndoCommands(int U)
{
    int n = sz(commands);
    commands.pb(commands[n - U - 1]);
}
char GetLetter(int P)
{
    int v = *commands.rbegin();
    for(int k = sz(trie[v].parent) - 1; k >= 0; k = min(k - 1, sz(trie[v].parent) - 1))
        if (trie[trie[v].parent[k]].h >= P ) v = trie[v].parent[k];
    return trie[v].val;
}
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