using System;

class PruebaSwap
{
    static void Swap(ref string a, ref string b)
    {
        string temp = a;
        a = b;
        b = temp;
    }

    static void Main()
    {
        string x = "Juan";
        string y = "Oliva";
        Swap(ref x, ref y);
        Console.WriteLine(x);   // Oliva
        Console.WriteLine(y);   // Juan
    }
}