#include <stdio.h>
#include <string.h>

int main(void) {
    int i, n, d, sum;
    char s[50001];

    scanf("%d %d", &n, &d);
    sum = 0;

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

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