using System;
using System.Collections.Generic;
using System.Linq;
public static class Fibonacci
{
public static IEnumerable<ulong> Enumerate()
{
var mem = new ulong[] { 1, 0 };
for (byte b = 0; ; b ^= 1)
yield return mem[b] += mem[1 - b];
}
public static ulong ValueAt(int n) => Enumerate().Skip(n - 1).First();
}
class MainClass {
static void Main() {
//any number over n = 93 is too big for ulong; therefore, I use BigInteger in .NET Framework
//I should implement my own BigInteger here, but I'm just too lazy for now ;)
var n = 1;
foreach(var value in Fibonacci.Enumerate().Take(93))
Console.WriteLine($"{n++}: {value}");
}
}
