def climb_stairs(k):
    """
    Return the number of ways that `k` stairs can be climbed
    given that you can climb either 1 or 2 stairs at a time
    """
    num_ways = [1]

    for idx in range(1, k+1):
        one_step = num_ways[idx-1]
        two_step = num_ways[idx-2] if idx > 1 else 0
        num_ways.append(one_step + two_step)

    return num_ways[-1]