Delegate composition pipeline

Implement static Func<string, string> Pipeline(params Func<string, string>[] steps) returning one delegate applying steps left to right (step 1 first). Also implement static Func<int> Memoize(Func<int> f) — no, simpler: implement static int InvokeThrice(Func<int> f) that calls f exactly three times and returns the last result (tests that delegates are first-class values).