#include <bits/stdc++.h>
using namespace std;
struct state{
int curl;
char curc;
state* par;
};
vector<state> states;
state cs;
void Init() {
cs.curl=-1;
cs.curc=' ';
cs.par=nullptr;
states.push_back(cs);
}
void TypeLetter(char L) {
state x;
x.curl=cs.curl+1;
x.curc=L;
x.par=&states[states.size()-1];
states.push_back(x);
cs=x;
}
void UndoCommands(int U) {
state x;
x.curl=states[states.size()-U-1].curl;
x.curc=states[states.size()-U-1].curc;
x.par=&states[states.size()-U-1];
states.push_back(x);
cs=states.back();
}
char GetLetter(int P) {
state tmp=cs;
while(tmp.curl!=P)tmp=*tmp.par;
return tmp.curc;
}
