#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
struct node
{
int l = 0;
int r = (1 << 20)-1;
node* left;
node* right;
bool is_son = 0;
int siz_ = 0;
char val = 'a';
void get_son()
{
if(!is_son)
{
left = new node;
left -> l = l;
left -> r = (l+r)/2;
right = new node;
right -> l = (l+r)/2+1;
right -> r = r;
}
is_son = 1;
}
char get_val(int poz)
{
if(l == r) return val;
if((l+r)/2 >= poz) return left -> get_val(poz);
return right -> get_val(poz);
}
void add(int poz, node* prev, int x)
{
if(l == r)
{
val = x;
return;
}
prev -> get_son();
is_son = 1;
if(poz <= (l+r)/2)
{
right = prev -> right;
left = new node;
left -> l = l;
left -> r = (l+r)/2;
left -> add(poz,prev->left,x);
}
else
{
left = prev -> left;
right = new node;
right -> l = (l+r)/2+1;
right -> r = r;
right -> add(poz,prev->right,x);
}
}
};
vector<node> nodes;
void Init()
{
node xd;
nodes.pb(xd);
}
void TypeLetter(char L)
{
node xd2;
xd2.add(nodes.back().siz_,&nodes.back(),L);
xd2.siz_ = nodes.back().siz_+1;
nodes.pb(xd2);
}
void UndoCommands(int U)
{
nodes.pb(nodes[siz(nodes)-1-U]);
}
char GetLetter(int P)
{
return nodes.back().get_val(P);
}
