text: int Solution::climbStairs(int n) {
  	if (n < 3) {
  		return n;
  	}
  	vector<int> ans(n + 1);
  	ans[1] = 1;
  	ans[2] = 2;
  	for (int i = 3; i <= n; i++) {
  		ans[i] = ans[i - 1] + ans[i - 2];
  	}
  	return ans[n];
  }
  