#include<bits/stdc++.h>
using namespace std;


int main()
{
	ios_base::sync_with_stdio(0);
	long long a,b,c;
	int pol = 0;
	cin >> a >> b >> c;
	for(int i = 0;i < c;++i)
	{
		if(b*2+((pol*2)/10) > a)
		{
			if(a%2 == 1)
			{
				if(pol == 5)
				{
					b += (a/2)+1;
					pol = 0;
				}
				else
				{
					b += a/2;
					pol = 5;
				}
				cout << b << '.' << pol;
				return 0;
			}
			else
			{
				b += a/2;
				cout << b << '.' << pol;
				return 0;
			}
		}
		else
		{
			a -= b*2+((pol*2)/10);
			b *= 2;
			if(pol == 5)
			{
				b++;
				pol = 0;
			}
		}
	}
	cout << b << '.' << pol;
}