爬楼梯

class Solution {
public:
    /**
     * @param n: An integer
     * @return: An integer
     */
    int climbStairs(int n) {
        // write your code here
        // write your code here
int one = 0;
int two = 1;
while(n>0) {
two=one+two;
one=two-one;
n--;
}
return two;

    }
};