3. 費氏數列

using System.Numerics; // 我說不算就不算

long[] fib = new long[93];
fib[0] = 0;
fib[1] = 1;
Console.WriteLine($"{0 + 1} {fib[0]}");
Console.WriteLine($"{1 + 1} {fib[1]}");
for (int i = 2; i < 93; i++)
{
    fib[i] = fib[i - 1] + fib[i - 2];
    Console.WriteLine($"{i + 1} {fib[i]}");
}
Console.Write("請從費氏數列(Fibonacci Sequence)中選擇第1個數:");
int a = int.Parse(Console.ReadLine());
Console.WriteLine($"您選擇第 {a} 費氏數列(Fibonacci Sequence):     {fib[a]}");
Console.Write("請從費氏數列(Fibonacci Sequence)中選擇第2個數:");
int b = int.Parse(Console.ReadLine());
Console.WriteLine($"您選擇第 {b} 費氏數列(Fibonacci Sequence):     {fib[b]}");
Console.WriteLine($"兩個費氏數列(Fibonacci Sequence) 相加結果為: {new BigInteger(fib[b]) + new BigInteger(fib[a])}");