//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

//---------------------------------------------------------------------------

#pragma argsused
#include <stdio.h>
int main(int argc, char* argv[])
{
  int i;
  double d,s;
  while(scanf("%lf",&d)>0)
  {
    s=d;
    for (i=1;i<12;i++)
    {
      scanf("%lf",&d);
      s+=d;
    }
    printf("$%.2lf\n",s/12);
  }
  return 0;
}
//---------------------------------------------------------------------------