class Solution {
public:
    int climbStairs(int n) {
        using namespace std;
      int a=1,b=1,number=0;
        if(n==0||n==1)
        {
            return 1;
        }
        while(n>1)
        {
            number=a+b;
            a=b;
            b=number;
            n--;
        }
        return number;
    }
};