#include<stdio.h>
#include<string.h>
int main()
{
	float a[13],b=0.0;
	int i;
	memset(a,0.0,13);
	for (i=0;i<12;i++)
	{
		scanf("%f",&a[i]);
		b=b+a[i];
	}
	b=b/12.0;
	printf("$%.2f\n",b+0.005);
	return 0;
}