static void HoanVi(ref int a, ref int b)
public static void Main()
Console.WriteLine("Nhap a : ");
a = int.Parse(Console.ReadLine());
Console.WriteLine("Nhap b: ");
b = int.Parse(Console.ReadLine());
Console.WriteLine("a truoc khi hoan vi la: {0}", a);
Console.WriteLine("b truoc khi hoan vi la: {0}", b);
Console.WriteLine("-----------------------------------------");
Console.WriteLine("a sau khi hoan vi la: {0}", a);
Console.WriteLine("b sau khi hoan vi la: {0}", b);