---

def H(num, fr, to, aux):
    if num == 1:
        #print
        return (f' {fr} -> {to},')
    else:
        s = ''
        s = H(num - 1, fr, aux, to)
        s = s + (f' {fr} -> {to},')
        s = s + H(num - 1, aux, to, fr)
        return s

if __name__ == '__main__':
    print(H(3,1,2,3))