KTPM K10

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace So
{
    class Program
    {

    /*
    ham kiem tra mot so co phai la so nguyen to khong.
    so nguyen to la so chi co 2 uoc la 1 va chinh no (2, 3, 5, 7, ...)
    */
        public static bool ktNT(int n)
        {

            if (n < 2)
            {
                return false;
            }

            for (int i = 2; i <= Math.Sqrt(n); i++ )
            {
                if (n % i == 0)
                {
                    return false;
                }
            }

            return true;
        }

    /*
    ham kiem tra mot so co phai la so chinh phuong khong.
    so chinh phuong la so chi co can bac 2 cua no la mot so nguyen (4, 9, 16, ...)
    */
        public static bool ktCP(int n)
        {
            double can = Math.Sqrt(n);

            if (can == (int)can)
            {
                return true;
            }
            return false;
        }


    /*
    ham kiem tra mot so co phai la so hoan hao khong.
    so hoan hao la so co tong cac uoc nho hon no bang chinh no (6, 28, ...)
    */
        public static bool ktHH(int n)
        {
            int tong = 0;

            for (int i = 1; i < n; i++)
            {
                if (n % i == 0)
                {
                    tong = tong + i;
                }
            }

            if (tong == n)
            {
                return true;
            }
            return false;
        }


    /*
    ham tinh tong cac so nguyen to trong khoang tu a den b.
    */
        public static  int tongNT(int a, int b)
        {
            int tong = 0;
            for (int i = a; i <= b; i++)
            {
                if (ktNT(i))
                {
                    tong = tong + i;
                }
            }
            return tong;
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Nhap 2 so ban can kiem tra: ");
            int a = Convert.ToInt16(Console.ReadLine());
            int b = Convert.ToInt16(Console.ReadLine());

            Console.WriteLine("Tong cac so nguyen to tu a den b la: " + tongNT(a, b));

            Console.ReadLine();
        }

    }
}