Oldingi va keyingi Fibonachchi

Fibonachchi ketma-ketligiga (1, 1, 2, 3, 5, 8, …) tegishli N > 1 soni berilgan. Ketma-ketlikdagi undan oldingi va undan keyingi sonni "prev=<oldingi>, next=<keyingi>" ko'rinishidagi satr sifatida qaytaring.

func prevAndNextFib(N int) string {
    // ...
}

Misollar

Input: N=8
Output: "prev=5, next=13"

Input: N=21
Output: "prev=13, next=34"

Input: N=1
Output: "prev=0, next=1"

Maslahatlar

1. a, b := 0, 1 dan boshlab b != N bo'lguncha a, b = b, a+b qiling.
2. Tugagach a — oldingi, a + b — keyingi son.