1. /**
    2.  * @param n: an integer
    3.  * @return: an ineger f(n)
    4.  */
    5. func Fibonacci(n int) int {
    6.     // write your code here
    7.     q, p := 0, 1
    8.     if n <= 1 {
    9.         return n - 1
    10.     }
    11.     for i := 2; i < n; i++ {
    12.         sum := q + p
    13.         q = p
    14.         p = sum
    15.     }
    16.     return p
    17. }