/*
One can reach i^{th}i th step in one of the two ways:

Taking a single step from (i-1)^{th}(i−1)th step.

Taking a step of 22 from (i-2)^{th}(i−2)th step.

*/

class Solution {
    public int climbStairs(int n) {
        if(n == 1) return 1;
        
        int [] dp = new int[n+1];
        dp[1] = 1;
        dp[2] = 2;
        
        for(int i=3; i<=n; i++)
        {
            dp[i] = dp[i-1] + dp[i-2];
        }
        return dp[n];
    }
}