#include <stdio.h>
#include <math.h>

int main(){
  int tint=0;
  
  for(int i=0;i<12;i++){
    char line[100];
    fgets(line, 100, stdin);
    int d,p;
    sscanf(line, "%i.%i", &d, &p);
    tint += d*100 + p;
  }

  tint = (int) rint(tint/12.0);

  printf("$%i.%02i\n", tint/100, tint%100);

}