alph = 'ko'
c = 0 #счетчик букв к
for f in range(2):
    if f == 0:
        c += 1
    for s in range(2):
        if s == 1 and f == 1:
            continue
        if s == 0:
            c += 1
        for t in range(2):
            if t == 1 and s == 1:
                continue
            if c == 2 and t == 0:
                continue
            print(alph[f] + alph[s] + alph[t])
        if s == 0:
            c -= 1
    if f == 0:
        c -= 1