#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,d;
signed main(){
	scanf("%lld%lld",&n,&d);
	while(n){
		if(d!=0&&d/n<2)printf("A"),d--;
		else if(d!=0&&d/n==2)printf("B"),d-=2;
		else printf("C");
		n--;
	}
	return 0;
}