//#include "richest.h"
#pragma GCC optimize("Ofast,unroll-loops")
#include<bits/stdc++.h>
//#define int long long
#define ll long long
#define down cout<<'\n';
#define debug cout<<" cucuucucuuu",down
#define modwwe int t;cin>>t; while(t--)
#define bit(i,j) (i>>j&1)
#define sobit(a) __builtin_popcountll(a)
#define task2 "top1tst"
#define task "test"
#define fin(x) freopen(x".inp","r",stdin)
#define fou(x) freopen(x".out","w",stdout)
#define pb push_back
#define mask(k) (1ll<<k)
#define checktime cerr << (double)clock() / CLOCKS_PER_SEC * 1000 << " ms";
using namespace std;
#define getchar_unlocked getchar
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
int rand(int l,int r)
{
return uniform_int_distribution<int>(l,r)(rd);
}
void phongbeo();
const ll inf=1e9;
const int mod2 = 998244353;
//const int base=67;
ll n, m, s1, s2, s4, s3, sf, k, s5, s6, mx, s7, s8, s9, mx2, res, dem2 = 0, dem = 0, s33, dem3, dem4, mid, l2, r2, center;
ll i, s10, s12,k1,k2,k3,s11,lim,w,l,r,dem5,dem6,dem7,dem9,now,root,q,start,en,t,cost,cen;
ll kk;
ll el = 19;
string c[26];
int query(string str);
string solve(int l,int r)
{
if(l==r)return c[l];
int mid=l+r>>1;
string lft=solve(l,mid),rgt=solve(mid+1,r);
string hehe;
dem=0;
string kk;
for(int i=0; i<lft.size(); i++)
{
if(dem==rgt.size())
{
hehe=hehe+lft[i];
continue;
}
kk="";
for(int j=dem; j<rgt.size(); j++)
kk=kk+rgt[j];
s2=query(hehe+lft[i]+kk);
if(s2!=hehe.size()+1+kk.size())
{
hehe=hehe+rgt[dem];
i--;
dem++;
}
else
{
hehe=hehe+lft[i];
}
}
for(int j=dem; j<rgt.size(); j++)
hehe=hehe+rgt[j];
return hehe;
}
string guess(int n, int s)
{
for(int j=0; j<s; j++)
{
string hehe;
for(int i=0; i<n; i++)
hehe=hehe+char('a'+j);
s2=query(hehe);
c[j]="";
for(int i=0; i<s2; i++)c[j]=c[j]+char('a'+j);
}
return solve(0,s-1);
}
