package main

import . "fmt"
import . "strings"

func main() {
	var n, d int
	Scan(&n, &d)
	for a := n; a >= 0; a-- {
		b := (d - a) / 2
		if b < 0 || a + b > n || a+2*b != d {
			continue
		}
		c := n - (a+b)
		ans := Repeat("A",a)+Repeat("B",b)+Repeat("C",c)
		Println(ans)
		return
	}
}