func fibonacci22(n int) int {
	f := make([]int, n+1, n+2)
	if n < 2 {
		f = f[0:2]
	}
	f[0] = 0
	f[1] = 1
	for i := 2; i <= n; i++ {
		f[i] = f[i-1] + f[i-2]
	}
	return f[n]
}

func fibonacci2(n int) int {
	x, y := 0, 1
	for i := 2; i <= n; i++ {
		x, y = y, x+y
	}
	return y
}

func fibo2(n int) int {
	if n < 2 {
		return n
	}
	return fibo2(n-1) + fibo2(n-2)
}