using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static void Main(String[] args) {
		string[] temp = Console.ReadLine().Split(' ');
		
		double a = Convert.ToDouble(temp[0]);
		double b = Convert.ToDouble(temp[1]);
		double t = Convert.ToDouble(temp[2]);
		
		double cof = (a+b)/2;
		double up_per_mc = Math.Pow(cof, t);
		

		Console.WriteLine(up_per_mc);
    }
}