#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " :: " << x << endl;
#define _ << " " <<
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define SZ(x) ((int)(x).size())
typedef pair<int,int> ii;
int query(string str);
int N;
const int mxS = 26;
char alpha[mxS];
string guess(int _N, int S) {
N = _N;
FOR(i,0,S-1) alpha[i] = 'a' + i;
vector<ii> freq;
FOR(i,0,S-1) {
string s(N,alpha[i]);
int f = query(s);
freq.emplace_back(f,i);
//~ cout << f << ' ';
}
//~ cout << endl;
string s(freq[0].first,alpha[freq[0].second]);
FOR(i,1,SZ(freq)-1){
FOR(j,1,freq[i].first){
FOR(k,0,SZ(s)){
string t = s.substr(0,k) + alpha[freq[i].second] + s.substr(k);
int x = query(t);
if (x == SZ(t)) { s = t; break; }
}
}
//TRACE(s);
}
return s;
}
