#include <iostream>
#include <cmath>

using namespace std;

int main()
{
	double a;	// factor a
	double b;	// factor b
	double t;	// time in ms
	double y;	// viral particles
	
	do
	{
		cin >> a >> b >> t;
	}
	while(a <= 1 && a >= 100 &&
		  b <= 1 && b >= 100 &&
		  t <= 1 && t >= pow(10, 18));
	
	y = 0.5 * a + 0.5 * b;
	y = fmod(y, (pow(10, 9) + 7));
	
	cout << y << endl;
	
	return 0;
}