#include<stdio.h>
int main()
{
	double mmoney[12];
	double sum=0.0,ave;
	int i=12;
	while(i--)
	{
	   scanf("%lf",&mmoney[i]);
           sum=sum+mmoney[i];
	}
	ave=sum/12;
	printf("$%.2lf\n",ave);
	return 0;

}