Fibonacci killer

gistfile1.cs

using System;

public class FibonacciKillerKata : IFibonacciKillerKata
{
    public int Fibonacci(int n)
    {
        if (n <= 1) return n;
        else return Fibonacci(n-1) + Fibonacci(n-2);
    }
}

public interface IFibonacciKillerKata
{
    /// <summary>
    /// Calculate an element of the Fibonacci sequence
    /// </summary>
    /// <param name="n">element number</param>
    /// <returns>n-th element of the Fibonacci sequence</returns>
    int Fibonacci(int n);
}