leetcode_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?

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