#include <bits/stdc++.h>
#define all(x) x.begin(), x.end()
#define lc (i << 1)
#define rc (i << 1 | 1)
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const int MN = 1e6 + 5, LN = 17, MOD = 1e9 + 7, INF = 0x3f3f3f3f, BSZ = 320;
char s[MN];
int spt[MN][20], dep[MN];
int cur;
void Init() {
}
void TypeLetter(char L) {
cur++;
s[cur] = L;
spt[cur][0] = cur - 1;
dep[cur] = dep[cur - 1] + 1;
for (int j = 1; j < LN; j++)
spt[cur][j] = spt[spt[cur][j - 1]][j - 1];
}
void UndoCommands(int U) {
int last = cur - U;
cur++;
s[cur] = s[last];
int par = spt[last][0];
spt[cur][0] = par;
dep[cur] = dep[par] + 1;
for (int j = 1; j < LN; j++)
spt[cur][j] = spt[spt[cur][j - 1]][j - 1];
}
char GetLetter(int P) {
int now = cur;
for (int j = LN - 1; j >= 0; j--)
if (dep[spt[now][j]] >= P)
now = spt[now][j];
return s[now];
}
