#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <valarray>
#include <vector>

#define N 1000
#define MOD 1000000007
#define pe(str) return cout<<(str)<<endl,0
#define px(str) {cout<<(str)<<endl;exit(0);}
#define re(i,n) for(int i=0;i<(n);i++)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define fe(i,n,f) for_each(i,n,f)
#define bw(a,b,c) (((a)<=(b))&&((b)<=(c)))
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;

int main(void){
	int n,d;
	int m=0;
	std::multiset<char> s;
	cin>>n>>d;
	if(d>n){
		re(i,d-n)s.insert('B');
		d=n;
	}
	int k=n-s.size();
	re(i,min(k,d))s.insert('A');
	k=n-s.size();
	re(i,k)s.insert('C');
	for(__typeof(s.begin()) it=s.begin();it!=s.end();it++){
		cout<<*it;
	}
	cout<<endl;

	return 0;
}