#include <stdio.h>

int main(){
	int len,hole;
	scanf("%d%d",&len,&hole);
	
	
   char s[50001];
   int sum = 0;

    for (int i = 0; i < len; ++i) {
        if (hole == sum){
        	s[i] = 'C';	
        }else if ((len - i - 1) * 2 >= hole - sum - 1) {
            s[i] = 'A';
            ++sum;
        } else {
            s[i] = 'B';
            sum += 2;
        }
    }

    s[len] = '\0';
    printf("%s\n", s);
	
}