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?Note: Given n will be a positive integer.

int climbStairs(int n) {    if (n<=0) return 0;    if (n==1) return 1;    if (n==2) return 2;        int one_step_before = 2;    int two_steps_before = 1;    int all_ways = 0;        for(int i=3; i<=n; i++) {        all_ways = one_step_before + two_steps_before;        two_steps_before = one_step_before;        one_step_before = all_ways;    }    return all_ways;}