PY01050 - KÝ TỰ A – B – C.py

def Try(s,n,a,b,c):
	if len(s) == n and a > 0 and a <= b and b <= c:
		print(s)
	if len(s) < n:
		Try(s+'A',n,a+1,b,c)
		Try(s+'B',n,a,b+1,c)
		Try(s+'C',n,a,b,c+1)
k = int(input())
for i in range(3,k+1):
	Try("",i,0,0,0)