#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 5, logn = 20;
struct cmd
{
bool undo;
int x, sum;
vector<int> pv;
char c;
};
vector<cmd> v;
void NewCommand() // spracuj ten nakonci v ak vies ze musis ist x znakov dozadu
{
cmd &c = v.back();
int x = c.x + 1;
int pv = v.size() - 1 - x;
c.pv.assign(logn, 0);
if (pv == -1) return;
c.sum += v[pv].sum;
if (v[pv].undo) pv = v[pv].pv[0];
c.pv[0] = pv;
for (int i = 1; i < logn; i++) c.pv[i] = v[c.pv[i-1]].pv[i-1];
}
void Init() {}
void TypeLetter(char L)
{
v.push_back({false, 0, 1, {}, L});
NewCommand();
}
void UndoCommands(int U)
{
v.push_back({true, U, 0, {}, '.'});
NewCommand();
}
char GetLetter(int P)
{
int num = v.back().sum, b = num - P;
int id = v.size() - 1;
if (!v[id].undo) b--;
for (int i = 0; i < logn; i++)
{
if ((1 << i) & b) id = v[id].pv[i];
}
return v[id].c;
}
