package main

func main() {

}

func climbStairs(n int) int {
	if n == 1 {
		return 1
	}
	if n == 2 {
		return 2
	}
	stepn1 := 1
	stepn2 := 2
	for i := 3; i <= n; i++ {
		current := stepn1 + stepn2
		stepn1, stepn2 = stepn2, current
	}
	return stepn2
}