#include <bits/stdc++.h>
using namespace std;
void Init() {}
const int N = 1e6 + 20, LOG = 20;
int n;
int up[N][LOG], dep[N];
char A[N];
void TypeLetter(char c) {
++n;
A[n] = c;
up[n][0] = n - 1;
dep[n] = dep[n-1] + 1;
for(int i = 1;i < LOG;i++)up[n][i] = up[up[n][i-1]][i-1];
}
void UndoCommands(int x) {
++n;
up[n][0] = n - x - 1;
dep[n] = dep[n - x - 1];
for(int i = 1;i < LOG;i++)up[n][i] = up[up[n][i-1]][i-1];
}
char GetLetter(int x) {
++x;
int u = n;
for(int i = LOG - 1;i >= 0;i--){
if(dep[up[u][i]] >= x){
u = up[u][i];
}
}
return A[u];
}