#include <cstdio>

const int MAX_N = 50000;

using namespace std;

int main()
{
    int n, d;
    char ans[MAX_N];
    
    scanf("%d%d", &n, &d);
    
    if (n >= d) {
        for (int i = 0; i < d; ++i) {
            ans[i] = 'A';
        }
        for (int i = d; i < n; ++i){
            ans[i] = 'C';
        }
    } else {
        int numB = d - n;
        for (int i = 0; i < n - numB; ++i) {
            ans[i] = 'A';
        }
        for (int i = n - numB; i < n; ++i) {
            ans[i] = 'B';
        }
    }
    
    for (int i = 0; i < n; ++i) {
        printf("%c", ans[i]);
    }
    printf("\n");
    
    return 0;
}