#include "combo.h"
using namespace std;
string ch = "ABXY";
string guess_sequence(int N) {
// Use 2 queries to find first character
string p = "";
for (int i = 0; i < 2*N; ++i) p += ch.substr(0, 2);
int c1, c2;
if (press(p)) c1 = 0, c2 = 1;
else c1 = 2, c2 = 3;
p = string(4*N, ch[c1]);
if (!press(p)) swap(c1, c2);
if (c1 != 0) swap(ch[0], ch[c1]);
string S(1, ch[0]); // build the answer in this string
// Use 1 query for all remaining characters except last one
for (int i = 1; i < N-1; ++i) {
p = S + ch[2];
for (int j = 1; j <= 3; ++j) p += S + ch[3] + ch[j];
while ((int)p.size() < 4*N) p.push_back(ch[0]);
int coins = press(p);
if (coins == i) S.push_back(ch[1]);
else if (coins == i+1) S.push_back(ch[2]);
else S.push_back(ch[3]); // coins == i+2
}
// Use final 2 queries to find last characters
p = S + ch[1];
while ((int)p.size() < 4*N) p.push_back(ch[0]);
if (press(p) == N) S.push_back(ch[1]);
else {
p[N-1] = ch[2];
if (press(p) == N) S.push_back(ch[2]);
else S.push_back(ch[3]);
}
return S;
}
