#include<bits/stdc++.h>
using namespace std;  
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
#define rep(i,n) for(ll i=0;i<(n);i++)  
#define pii pair<int,int>
#define piii pair<int,pii>
#define mp make_pair
#define pb push_back  
#define ALL(a) (a).begin(),(a).end()
#define FST first
#define SEC second  
const int INF = (INT_MAX/2);
const ll LINF = (LLONG_MAX/2);
const double eps = 1e-14;
const double PI = M_PI;  
#define DEB cout<<"!"<<endl
#define SHOW(a,b) cout<<(a)<<" "<<(b)<<endl
#define SHOWARRAY(ar,i,j) REP(a,i)REP(b,j)cout<<ar[a][b]<<((b==j-1)?((a==i-1)?("\n\n"):("\n")):(" "))
  
#define DIV 1000000007

typedef vector<ll> Array;
typedef vector<Array> matrix;


int main(){
  int N,D; cin >> N >> D;
  string ans = "";
  
  for(;N != 0;){
    if(D && D < 2*N){
      ans += 'A';
      D--;
    }else if(D){
      ans += 'B';
      D--;D--;
    }else{
      ans += 'C';
    }
    N--;
  }
  
  cout <<ans << endl;
  
  return 0;
}