using System;

public class Program

{

    public static void Main()

    {

        {

            int chon;

            do

        {

            Console.Clear();

            Console.Write("1- Nhap vao 2 so m, n, xuat ra nhung so chia het cho 7 trong khoang tu n den m. \n ");

            Console.Write("2- Nhap vao so a, b và n. xuat ra nhung so ma a và b deu chia het cho so do trong khoang tu 1 đến n. \n ");

            Console.Write("3- Nhap vao so n, xuat ra n so fibonacy dau tien. \n ");

            Console.Write("4- Nhap vao so n, xuat ra n so nguyen to dau tien. \n ");

            Console.Write("0- Thoat. \n ");

            chon = Convert.ToInt32(Console.ReadLine());

            switch (chon)

            {

            /*Bai Tap 1*/

                case '1':

                {

                    int m, n;

                    Console.Write("Nhap vao so m: ");

                    m = Convert.ToInt32(Console.ReadLine());

                    Console.Write("Nhap vao so n: ");

                    n = Convert.ToInt32(Console.ReadLine());

                    if (m < n)

                    {

                        Console.WriteLine("Cac so chia het cho 7 tu " + n + " den " + m + " la: ");

                        for (int k = m; k <= n; k++)

                    {

                        if (k % 7 == 0)

                        Console.WriteLine(k);

                    else if (m > n)

                    {

                        Console.WriteLine("Cac so chia het cho 7 tu " + n + " den " + m + " la: ");

                        for (k = m; k <= n; k++)

                    {

                        if (k % 7 == 0)

                        Console.WriteLine(k);

                    }

                }

                    else

                    {

                    Console.WriteLine("Khong co so can tim!");

                    }

                            }

                        }

                    Console.WriteLine("\nNhap vao 1 phim bat ky de tiep tuc!");

                    Console.ReadLine();

                }

                    break;

        /*Bai Tap 2*/

                case '2':

​

                int a, b, n2;

                {

                    Console.Write("Nhap vao so a: ");

                    a = Convert.ToInt32(Console.ReadLine());

                    Console.Write("Nhap vao so b: ");

                    b = Convert.ToInt32(Console.ReadLine());

                    Console.Write("Nhap vao so n: ");

                    n2 = Convert.ToInt32(Console.ReadLine());

​

                    Console.WriteLine(" Nhung so ma " + a + " va " + b + " cung chia het tu 1 den " + n2 + " la: ");

                    for (int k = 1; k <= n2; k++)

                    {

                        if ((a % k == 0) && (b % k == 0))

                        Console.WriteLine(k);

                    }

                }

​

                        Console.WriteLine("\nNhap vao 1 phim bat ky de tiep tuc!");

                        Console.ReadLine();

                break;

​

/*Bai Tap 3*/

Console.Write("Bai Tap 3 \n ");

​

Console.Write("Nhap vao so n, xuat ra n so fibonacy dau tien. \n ");

​

int n3, f1, f2, fk;

            {

Console.Write("nhap vao bien n: ");

                n3 = Convert.ToInt32(Console.ReadLine());

​

if (n3 == 1)

Console.WriteLine(0);

​

else if (n3 == 2)

Console.WriteLine("0 1");

​

else if (n3 >= 3)

                {

                    f1 = 0;

                    f2 = 1;

Console.Write(f1 + " " + f2);

​

​

for (int i = 3; i <= n3; i++)

                    {

fk = f1 + f2;

                        f1 = f2;

                        f2 = fk;

​

Console.Write(" " + fk);

                    }

​

Console.WriteLine("\nNhap vao 1 phim bat ky de tiep tuc!");

Console.ReadLine();

​

/*Bai tap 4*/

​

                    {

                        {

Console.Write("Bai Tap 4 \n ");

​

Console.Write("Nhap vao so n, xuat ra n so nguyen to dau tien. \n ");

​

int n4, i, ctr, bat_dau, ket_thuc;

​

​

Console.Write("Nhap so bat dau cua day: ");

                            bat_dau = Convert.ToInt32(Console.ReadLine());

Console.Write("Nhap so ket thuc cua day: ");

                            ket_thuc = Convert.ToInt32(Console.ReadLine());

Console.Write("Cac so nguyen to trong day tu {0} toi {1} la: \n", bat_dau, ket_thuc);

​

for (n4 = bat_dau; n4 <= ket_thuc; n4++)

                            {

ctr = 0;

​

for (i = 2; i < n4; i++)

                                {

if (n4 % i == 0)

                                    {

ctr++;

break;

                                    }

                                }

​

if (ctr == 0 && n4 != 1)

Console.Write("{0} ", n4);

Console.ReadLine();

                        }

                    }

                    }}}}}

​