#include <iostream>
#include <stdlib.h>
using namespace std;

int main(void)
{
	double sum=0;
	double monthIn = 0;
	for (int i = 0; i < 12; i++){
		cin >> monthIn;
		sum += monthIn;
	}
	printf("$%.2f\n", sum / 12);
	system("pause");
	return 0;
}