#include <bits/stdc++.h>
//#include "combo.h"
using namespace std;
int press ( string p );
string guess_sequence ( int N ) {
int n = N;
string answer = "";
vector <string> v( 4 );
v = { "A", "B", "X", "Y" };
if ( n == 1 ) {
if ( press( "A" ) == 1 ) {
return "A";
} else if ( press( "B" ) == 1 ) {
return "B";
} else if ( press( "X" ) == 1 ) {
return "X";
} else {
return "Y";
}
}
for ( int i = 0; i < n; i++ ) {
string s = "";
if ( i == 0 ) {
if ( press( "AB" ) > 0 ) {
if ( press ( "A" ) == 1 ) {
answer = "A";
v.erase( v.begin() );
} else {
answer = "B";
v.erase( v.begin() + 1 );
}
} else {
if ( press( "X" ) == 1 ) {
answer = "X";
v.erase( v.begin() + 2 );
} else {
answer = "Y";
v.erase( v.begin() + 3 );
}
}
continue;
} else if ( i == n - 1 ) {
for ( int j = 0; j < 2; j++ ) {
if ( press( answer + v[j] ) == n ) {
answer += v[j];
break;
}
}
if ( answer.length() != n ) {
answer += v[2];
}
continue;
} else {
for ( int j = 0; j < 2; j++ ) {
if ( j == 0 ) {
s = answer + v[j];
} else {
for ( int z = 0; z < 3; z++ ) {
s += answer + v[j] + v[z];
}
}
}
int k = press( s );
if ( k == answer.length() ) {
answer += v[2];
} else if ( k == answer.length() + 1 ) {
answer += v[0];
} else {
answer += v[1];
}
}
}
return answer;
}
/*
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <string>
namespace {
constexpr int MAX_N = 2000;
constexpr int MAX_NUM_MOVES = 8000;
int N;
std::string S;
int num_moves;
void wrong_answer(const char *MSG) {
printf("Wrong Answer: %s\n", MSG);
exit(0);
}
} // namespace
int press(std::string p) {
if (++num_moves > MAX_NUM_MOVES) {
wrong_answer("too many moves");
}
int len = p.length();
if (len > 4 * N) {
wrong_answer("invalid press");
}
for (int i = 0; i < len; ++i) {
if (p[i] != 'A' && p[i] != 'B' && p[i] != 'X' && p[i] != 'Y') {
wrong_answer("invalid press");
}
}
int coins = 0;
for (int i = 0, j = 0; i < len; ++i) {
if (j < N && S[j] == p[i]) {
++j;
} else if (S[0] == p[i]) {
j = 1;
} else {
j = 0;
}
coins = std::max(coins, j);
}
return coins;
}
int main() {
char buffer[MAX_N + 1];
if (scanf("%s", buffer) != 1) {
fprintf(stderr, "Error while reading input\n");
exit(1);
}
S = buffer;
N = S.length();
num_moves = 0;
std::string answer = guess_sequence(N);
if (answer != S) {
wrong_answer("wrong guess");
exit(0);
}
printf("Accepted: %d\n", num_moves);
return 0;
}
*/
