/* author : TIT_manh */ #include <iostream> #include <vector> #include <string> #include <algorithm> #include <cmath> #include <iomanip> #include <cstdio> #include <cstdlib> #include <cstring> #include <map> #include <unordered_map> #include <set> #include <unordered_set> #include <queue> #include <stack> #include <deque> #include <bitset> #include <numeric> #include <functional> #include <cassert> #include <sstream> #include <climits> #define ll long long #define FOR(i,l,r) for (int i = l; i <= r; i++) #define FOD(i,r,l) for (int i = r; i >= l; i--) #define fi first #define se second #define pb push_back #define endl "\n" using namespace std; int n; char d[4] = {'A', 'B', 'X', 'Y'}; int press(string p); string guess_sequence(int N) { char first; string res = ""; if (press("A") == 1) { first = 'A'; res += 'A'; } else if (press("B") == 1) { first = 'B'; res += 'B'; } else if (press("X") == 1) { first = 'X'; res += 'X'; } else if (press("Y") == 1) { first = 'Y'; res += 'Y'; } if (N == 1) return res; FOR(tt,2,N) { FOR(i,0,3) if (d[i] != first) { res += d[i]; if (press(res) == tt) break; res.erase(res.size() - 1, 1); } } return res; }