#! /usr/local/bin/python3

def hanoi1(n, a, b, c):
    if n == 0:
        return
    yield from hanoi1(n-1, a, c, b)
    yield a, b
    yield from hanoi1(n-1, c, b, a)

def hanoi(n):
    yield from hanoi1(n, 'a', 'b', 'c')

for a, b in hanoi(7):
    print(f'{a} => {b}')