#include <bits/stdc++.h>
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define FORd(i, a, b) for (int i = (a); i >= (b); i--)
#define REP(i, n) FOR(i, 0, n)
using namespace std;
struct node {
node* ch[30];
node* par;
char c;
node(node* n, char cc) {
REP(i, 30) ch[i] = 0;
par = n, c = cc;
}
};
node* root;
vector <node*> ve;
int flag;
string s;
void Init() {
root = new node(NULL, '.');
ve.push_back(root);
return;
}
void TypeLetter(char L) {
flag = 1;
int x = (L - 'a');
if (!root->ch[x]) root->ch[x] = new node(root, L);
root = root->ch[x];
ve.push_back(root);
return;
}
void UndoCommands(int U) {
flag = 1;
root = ve[ve.size() - 1 - U];
ve.push_back(root);
return;
}
char GetLetter(int P) {
if (flag) {
s = "";
node* curr = root;
while (curr) {
s = s + curr->c;
curr = curr->par;
}
reverse(s.begin(), s.end());
flag = 0;
}
return s[P + 1];
}
