70. Climbing Stairs
You are climbing a stair case. It takes n steps to reach to the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
Note: Given n will be a positive integer.
思路：到第ｎ个台阶的迈法种数＝到第ｎ－１个台阶的迈法种数（再往上迈一步）＋到第ｎ－２个台阶的迈法种数（再往上迈两步）。斐波那契数列的问题。
