//#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;
#define debug(s) cout<< #s <<" = "<< s <<endl
#define all(v) (v).begin(), (v).end()
#define KeepUnique(v) (v).erase( unique(all(v)), v.end() )
#define MEMSET(a,val) memset(a, val, sizeof a)
#define PB push_back
#define endl '\n'
inline int myrand(int l, int r) {
int ret = rand(); ret <<= 15; ret ^= rand();
if(ret < 0) ret = -ret; ret %= (r-l+1); ret += l;
return ret;
}
template <typename F, typename S>
ostream& operator << (ostream& os, const pair< F, S>& p) {
return os<<"(" <<p.first<<", "<<p.second<<")"; }
typedef pair<int, int> ii;
template<typename T> using min_pq =
priority_queue<T, vector<T>, greater<T> >;
//int dx[] = {-1, +0, +1, +0};
//int dy[] = {+0, +1, +0, -1};
struct node {
int h, to[26], par;
char wot;
node() {
h = par = 0;
MEMSET(to, 0);
}
node(int p, int H, char w0t) {
h = H, par = p, wot = w0t;
MEMSET(to, 0);
}
};
deque<node> t(1);
void newnode(int &dir, int p, int H, char w0t) {
t.push_back(node(p,H,w0t));
dir = (int)t.size() - 1;
}
int version_cnt = 0;
int root;
int where[1000005];
int sp[20][1000005];
void add_node(int u, int p) {
sp[0][u] = p;
for(int i=1; i<=19; i++) {
sp[i][u] = sp[i-1][sp[i-1][u]];
}
}
int kth_parent(int u, int k) {
for(int i=19; i>=0; i--) {
if(k & (1 << i)) {
u = sp[i][u];
}
} return u;
}
void Init() {
newnode(where[version_cnt], 0, 0, 'a');
}
void TypeLetter(char L) {
L -= 'a';
int u = where[version_cnt];
if(t[u].to[L] == 0) {
newnode(t[u].to[L], u, t[u].h + 1, L + 'a');
} version_cnt++;
where[version_cnt] = t[u].to[L];
u = where[version_cnt];
add_node(u, t[u].par);
}
void UndoCommands(int U) {
version_cnt++;
where[version_cnt] = where[version_cnt - U - 1];
}
char GetLetter(int P) {
P++;
int u = where[version_cnt];
return t[kth_parent(u, t[u].h - P)].wot;
}
