#include <bits/stdc++.h>
using namespace std;
#ifdef wambule
string cs;
int press(string s) {
int dr = 0;
for(int i = 0; i < s.size(); ++i) {
for(int j = i; j < min((int)s.size(), i + (int)cs.size()); ++j) {
if(s[j] != cs[j - i]) {
dr = max(dr, j - i);
break;
}
if(j + 1 == (int)s.size() || j + 1 == i + (int)cs.size()) {
dr = max(dr, j - i + 1);
}
}
}
return dr;
}
#else
#include "combo.h"
#endif
string s = "";
int ask(vector<string> v) {
assert(v.size() < 5);
string c = "";
for(string t : v) {
c += s + t;
}
return press(c) - (int)s.size();
}
string guess_sequence(int n) {
string c[] = {"X", "Y", "A", "B"};
s = "";
if(!ask({c[0], c[1]})) {
swap(c[0], c[2]);
swap(c[1], c[3]);
}
if(!ask({c[0]})) swap(c[0], c[1]);
s = c[0];
swap(c[0], c[3]);
if(n == 1) return s;
for(int i = 2; i < n; ++i) {
int x = ask({c[0] + c[0], c[0] + c[1], c[0] + c[2], c[1]});
if(x == 2) {
s += c[0];
} else if(x == 1) {
s += c[1];
} else {
s += c[2];
}
}
if(ask({c[0]})) s += c[0];
else if(ask({c[1]})) s += c[1];
else s += c[2];
return s;
}
#ifdef wambule
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
srand(time(0));
int y = 0;
while(true) {
if(0) {
string c[] = {"X", "Y", "A", "B"};
int x = rand() % 4;
swap(c[3], c[x]);
cs = c[3];
for(int i = 0; i < 2000; ++i) {
x = rand() % 3;
cs += c[x];
}
string t = guess_sequence(cs.size());
if(t != cs) {
cout << cs << "\n" << t << endl;
cin.get();
} else if(y % 1 == 0) {
cout << y << endl;
}
++y;
} else {
cin >> cs;
string t = guess_sequence(cs.size());
cout << "[" << (t == cs) << "] " << t << endl;
}
}
return 0;
}
#endif
