#include<stdio.h>

int main()
{
	float data[12]={0.00};
	float sum=0.00;
	float average=0.00;
	int i=0;
	for(i=0;i<12;i++)
	{
		scanf("%f",&data[i]);
		sum=data[i]+sum;
	}
	average=sum/12;
	printf("$%.2f",average);
	return 0;
}