using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
foreach (int i in Fib().Take(12))
Console.Write($"{i} ");
}
public static IEnumerable<int> Fib()
int prev = 0, next = 1;
yield return prev;
yield return next;
while (true)
int sum = prev + next;
yield return sum;
prev = next;
next = sum;