using System;

​

// inspired by here: http://stackoverflow.com/a/3622173/420667

​

int Square(int x)

{

    return x*x;

}

​

int Diff(int n, Func<int, int> f)

{

    return f(n+1) - f(n);

}

​

Console.WriteLine(Diff(1, Square));

Console.WriteLine(Diff(1, (n) => Square(n)));