using System;

public class Test
{
        public static Func<T, TResult> MakeFunctionWithCounter<T, TResult>(Func<T, TResult> func)
        {
            int counter = 0;
            return t => { counter++; return func(t); };
        }

        public static int Counts<T, TResult>(Func<T, TResult> call)
        {
            return (int)call.Target.GetType().GetField("counter").GetValue(call.Target);
        }

        static void Main(string[] args)
        {
            var f = new Func<double, double>(d => d*d);
            f = MakeFunctionWithCounter(f);
            f(1);
            f(2);
            f(3);
            Console.WriteLine(Counts(f));
       }
}