#include <iostream.>
#include <iomanip>
using namespace std;
int main()
{
	double sum=0,n,ave=0;
	int i=0,k=0;
	for(i=0;i<12;i++)
	{
		cin>>n;
		sum+=n;
	}
	ave=sum/12;
	cout<<'$';
	if((ave-(int)ave)/0.01>0.5)
		ave+=0.01;
	cout<<setprecision(2)<<ave;
	return 0;
}