#include<stdio.h>
main()
{  long float a[12],b=0.0,c;
   int i;
   for(i=0;i<12;i++)
    { scanf("%lf",&a[i]);
      printf("\n");
      b+=a[i];
    }
   c=b/12.0;
   c=(int)(c*100+0.5);
   c=(long float)(c/100.0);
   printf("$%.2lf",c);
}