ans = ["AA"]
have = set(["AA"])
def f():
    if(len(have) == 26*26):
        for i in ans:
            print(i)
        exit()
    head = ans[-1][-1]
    for i in range(26):
        new = chr(ord("A") + i)
        if(head + new in have):continue
        ans.append(head + new)
        have.add(head + new)
        f()
        have.remove(head + new)
        ans.pop()
f()