// yukicoder: No.501 穴と文字列
// 2019.4.18 bal4u

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

#if 1
#define gc() getchar_unlocked()
#define pc(c) putchar_unlocked(c)
#else
#define gc() getchar()
#define pc(c) putchar(c)
#endif
int in()
{
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}

void outs(int w, int c) { while (w--) pc(c); }

int main()
{
	int N, D;
	N = in(), D = in();
	if (D > N) outs(2*N - D, 'A'), outs(D-N, 'B');
	else outs(D, 'A'), outs(N-D, 'C');
	pc('\n');
	return 0;
}