#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define sar(a,n) cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl
#define svec(v) cout<<#v<<":";rep(pachico,v.size())cout<<" "<<v[pachico];cout<<endl
#define svecp(v) cout<<#v<<":";each(pachico,v)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl
#define sset(s) cout<<#s<<":";each(pachico,s)cout<<" "<<pachico;cout<<endl
#define smap(m) cout<<#m<<":";each(pachico,m)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl
#define int long long

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 100005;

void solve(int a, int b, int c, int d, string& ans){
    int k = (a+b)/(b+1);
    int l = a / k;
    int r = a % k;
    int rem = b-l-(r!=0);
    int ed_pos = -1;
    int ed_num = -1;
    int ed_cnt = -1;
    int cri = -1;
    // cout << k << " " << l << " " << r << "\n";
    if(rem < 0){
        cri = 0;
    }else if(rem == 0){
        cri = 1;
    }else{
        if(r != 0){
            if(rem <= k-1+(r-1)*k){
                ed_pos = 1;
                if(rem <= k-1){
                    ed_num = 1;
                    ed_cnt = rem;
                }else{
                    rem -= k-1;
                    ed_num = (rem+k-1)/k+1;
                    ed_cnt = rem-(ed_num-2)*k;
                }
                rem = 0;
            }else{
                rem -= k-1+(r-1)*k;
            }
        }
        // show(r);
        // show(rem);
        if(ed_pos < 0){
            int syuki = k*(k-1)+k-1;
            ed_pos = (rem+syuki-1)/syuki+1;
            rem -= (ed_pos-2)*syuki;
            if(rem <= k-1){
                ed_num = 1;
                ed_cnt = rem;
            }else{
                rem -= k-1;
                ed_num = (rem+k-1)/k+1;
                ed_cnt = rem-(ed_num-2)*k;
            }
        }
        // cout << ed_pos << " " << ed_num << " " << ed_cnt << "\n";
        int rp = -1;
        if(ed_pos == 1){
            rp = (ed_num-1);
        }else{
            rp = r+(ed_pos-2)*k+(ed_num-1);
        }
        cri = rp*(k+1)+ed_cnt;
        if(ed_num == 1) cri++;
    }
    // show(cri);
    // [st,ed]
    int st = a+b-d+1;
    int ed = a+b-c+1;
    // cout << st << " " << ed << "\n";
    for(int j = st; j <= min(cri, ed); j++){
        if((j-1) % (k+1) == k){
            ans.pb('A');
        }else{
            ans.pb('B');
        }
    }
    for(int j = min(a+b-cri,d); j >= c; j--){
        if((j-1) % (k+1) == k){
            ans.pb('B');
        }else{
            ans.pb('A');
        }
    }
    reverse(all(ans));
    return;
}

signed main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int q;
    cin >> q;
    rep(i,q){
        int a,b,c,d;
        cin >> a >> b >> c >> d;
        string ans;
        if(a < b){
            solve(b,a,a+b+1-d,a+b+1-c,ans);
        }else{
            solve(a,b,c,d,ans);
        }
        if(a < b){
            reverse(all(ans));
            rep(i,len(ans)){
                if(ans[i] == 'A'){
                    cout << 'B';
                }else{
                    cout << 'A';
                }
            }
            cout << "\n";
        }else{
            cout << ans << "\n";
        }
    }
    return 0;
};


Measured memory_bytes: 384