#include <bits/stdc++.h>
using namespace std;

#define FOR(i,l,r) for(int i = (int) (l);i < (int) (r);i++)
#define ALL(x) x.begin(),x.end()
template<typename T> bool chmax(T& a,const T& b){ return a < b ? (a = b,true) : false; }
template<typename T> bool chmin(T& a,const T& b){ return b < a ? (a = b,true) : false; }
typedef long long ll;

int N,D;

int main()
{
	scanf("%d%d",&N,&D);
	int curr = 0;
	string ans;
	FOR(i,0,N){
		if(curr + 1 <= D && (D - (curr + 1)) <= (N - (i + 1)) * 2){
			ans += 'A';
			curr++;
		}
		else if(curr + 2 <= D && (D - (curr + 2)) <= (N - (i + 1)) * 2){
			ans += 'B';
			curr += 2;
		}
		else{
			ans += 'C';
		}
	}

	cout << ans << endl;

	return 0;
}