package main

import (
	"bufio"
	"os"
	"strconv"
	"strings"
)

func main() {
	stdin := bufio.NewScanner(os.Stdin)
	stdin.Scan()
	slice := strings.Split(stdin.Text(), " ")
	N, _ := strconv.Atoi(slice[0])
	D, _ := strconv.Atoi(slice[1])

	if D <= 0 {
		println("C")
	} else if D <= N {
		for i := 0; i < N; i++ {
			if i < D {
				print("A")
			} else {
				print("C")
			}
		}
	} else {
		for i := 0; i < N-(D-N); i++ {
			print("A")
		}
		for i := 0; i < (D - N); i++ {
			print("B")
		}
	}
}