#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int main() {
	int n, d;
	cin >> n >> d;
	
	string ans = "";
	while (n) {
		if (d == 0) ans += 'C';
		else {
			if (d - 1 <= 2 * (n - 1)) {
				ans += 'A';
				d--;
			}
			else {
				ans += 'B';
				d -= 2;
			}
		}
		n--;
	}
	
	cout << ans << endl;
	
	return 0;
}