Fibonacci Series and Factorial Program

Program to find Factorial of a given number and Fibonacci Series

Fibonacci Series

using System;
using System.Text;

namespace ProblemPractice
{
    //FIBONACCI SERIES
    class Program1
    {
        public static void Main(String[] args)
        {
           
            string str;
            do
            {
                Console.WriteLine("Press 1 for Fibnacci and 2 for Factorial :");
                int val = Int32.Parse(Console.ReadLine());
                if (val == 1)
                {
                    //Fibonacci
                    Fibonacci();
                }
                else if (val == 2)
                {
                    //Factorial
                    Console.WriteLine("Enter Value:");
                    int num = Int32.Parse(Console.ReadLine());
                    int factNum = Factorial(num);
                    Console.WriteLine(factNum);
                }
                else
                {
                    Console.WriteLine("Wrong option...Press any key to Exit.");
                }
                Console.WriteLine("Want to Continue, Press \"y\"");
                str = Console.ReadLine();
            } while (str == "y");
        }

        private static int Factorial(int num)
        {
            int fact;
            if (num == 1)
            {
                return 1;
            }
            else
            {
                fact= num * Factorial(num - 1);
                return fact;
            }
        }

        private static void Fibonacci()
        {
            int n = Int32.Parse(Console.ReadLine());
            int n1, n2, n3;
            n1 = 0; n2 = 1;
            int flag = 3;
            Console.Write(n1 + " " + n2 + " ");
            while (flag <= n)
            {
                n3 = n1 + n2;
                Console.Write(n3 + " ");
                n1 = n2;
                n2 = n3;
                flag++;
            }
            Console.WriteLine("");
        }
    }
}