#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=(n);i<(int) N;i++)
#define p(s) cout<<(s)<<endl
using namespace std;

int main() {
	int N,D;
	cin>>N>>D;
	string s="";
	if(N<=D){
		REP(i,0,2*N-D) s+='A';
		REP(i,0,D-N) s+='B';
	}else{
		REP(i,0,D) s+='A';
		REP(i,0,N-D) s+='C';
	}
	p(s);
	return 0;
}