#include<bits/stdc++.h> using namespace std; struct cmd { bool undo; int x; char c; }; string s; vector<cmd> v; bool rebuild = false; void Init() {} void TypeLetter(char L) { rebuild = true; v.push_back({false, 0, L}); } void UndoCommands(int U) { rebuild = true; v.push_back({true, U, '.'}); } char GetLetter(int P) { if (rebuild) { rebuild = false; s.clear(); for (int i = v.size() - 1; i >= 0; i--) { if (v[i].undo) i -= v[i].x; else s.push_back(v[i].c); } reverse(s.begin(), s.end()); //cout << s << endl; } return s[P]; }