public void TestCase()
{
var exch = new MoneyExchanger();
Assert.AreEqual(-1, exch.GetExchange(new int[] { 2 }, 3));
var coins = new int[] { 1, 2, 5 };
Assert.AreEqual(3, exch.GetExchange(coins, 11));
Assert.AreEqual(4, exch.GetExchange(coins, 13));
coins = new int[] { 2, 4, 5 };
Assert.AreEqual(5, exch.GetExchange(coins, 21));
Assert.AreEqual(-1, exch.GetExchange(new int[] { 2, 6 }, 15));
}
