/*
Task : combo
Author : Phumipat C. [MAGCARI]
Language: C++
Created : 17 May 2021 [12:41]
Algo :
Status :
*/
#include<bits/stdc++.h>
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x),end(x)
#define allst(x,y) (x).begin()+y,(x).end()
#define rmdup(x) (x).resize(unique((x).begin(),(x).end())-(x).begin())
#define sz(x) (int)(x).size()
#define decp(x) fixed << setprecision(x)
#define MOD (LL )(1e9+7)
using namespace std;
using LL = long long;
using PII = pair<int ,int >;
using PLL = pair<long long ,long long >;
const int dir4[2][4] = {{1,-1,0,0},{0,0,1,-1}};
const int dir8[2][8] = {{-1,-1,-1,0,1,1,1,0},{-1,0,1,1,-1,0,1,-1}};
LL modN(LL a,LL b,LL c = MOD){
if(b == 0) return 1;
if(b == 1) return a%c;
LL now = modN(a,b/2,c);
if(b&1) return (((now*now)%c)*(a%c))%c;
else return (now*now)%c;
}
#include "combo.h"
std::string guess_sequence(int N) {
vector<char > c(4);
vector<char >::iterator it;
c = {'A','B','X','Y'};
char last = 'Y';
it = c.begin();
int ret = 0;
string now;
c.pop_back();
now.push_back('0');
for(auto x:c){
now.back() = x;
ret = press(now);
if(ret){
c.erase(it);
break;
}
it++;
}
if(!ret) now.back() = last;
last = c.back();
c.pop_back();
rep(i,2,N+1){
now.push_back('0');
for(auto x:c){
now.back() = x;
ret = press(now);
if(ret == i) break;
}
if(ret!=i) now.back() = last;
}
// cout << now << '\n';
return now;
}
