#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
ll INF = 1e9+7;
ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ll,ii>
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
ll cur = 1;
ll nodes = 1;
ll depth[1000005];
char timi[1000005];
ll pos[1000005];
ll an[1000005][20];
void upd(ll x,ll p){
an[x][0] = p;
f(j,1,20){
an[x][j] = an[an[x][j-1]][j-1];
}
}
ll kth(ll a,ll k){
ll pos = 0;
ll ans = a;
while(k > 0){
if(k % 2){
ans = an[ans][pos];
}
pos++;
k /= 2;
}
return ans;
}
void Init(){
pos[0] = 0;
memset(an,0,sizeof an);
depth[0] = -1;
timi[0] = '$';
}
void TypeLetter(char L){
ll p = pos[cur-1];
depth[nodes] = depth[p] + 1;
upd(nodes,p);
timi[nodes] = L;
pos[cur] = nodes;
cur++;
nodes++;
}
void UndoCommands(int U){
pos[cur] = pos[cur - U - 1];
cur++;
}
char GetLetter(int P){
ll CUR = pos[cur-1];
///P = depth[ans]
///=> ans = kth(CUR,depth[CUR] - P)
assert(depth[CUR] >= P);
char ans = timi[kth(CUR,depth[CUR] - P)];
return ans;
}
