#include<bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
typedef long long LL;
int A,B,C;
int N;
int D;
int main(){
	cin>>N>>D;
	B=max(D-N,0);
	A=D-2*B;
	C=N-B-A;
	REP(i,A){
	    cout<<"A";
	}
	REP(i,B){
	    cout<<"B";
	}
	REP(i,C){
	    cout<<"C";
	}
        cout<<endl;
	return(0);
}