#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#define REP(i, n) for (ll i = 0; i < n; i++)
#define REP1(i, n) for (ll i = 1; i <= n; i++)
#define RREP(i, n) for (ll i = n - 1; i >= 0; i--)
#define RREP1(i, n) for (ll i = n; i >= 1; i--)
#define FOR(i, a, b, c) for (ll i = a; i <= b; i += c)
#define RFOR(i, a, b, c) for (ll i = a; i >= b; i -= c)
#define MAX(a, b) (a > b ? a : b)
#define MIN(a, b) (a < b ? a : b)
#define INF 1145141919
typedef long long ll;

int n, d;
char s[50001];

bool dfs(int idx, int sum) {
    if (idx == n) return sum == d;
    if (sum > d) return false;
    if (dfs(idx + 1, sum + 1)) { s[idx] = 'A'; return true; }
    else if (dfs(idx + 1, sum)) { s[idx] = 'C'; return true; }
    else if (dfs(idx + 1, sum + 2)) { s[idx] = 'B'; return true; }
    return false;
}

int main() {
    scanf("%d %d", &n, &d);
    dfs(0, 0);
    REP(i, n) putchar(s[i]);
    return 0;
}