#include <stdio.h>
#include <stdlib.h>
int cmp(const void *a, const void *b)
{
  return (*(int*)a)-(*(int*)b);
}
int main()
{
  int S[6];
  scanf("%d %d %d %d %d %d",S,S+1,S+2,S+3,S+4,S+5);
  qsort(S,6,sizeof(int),cmp);
  int i;
  int sum = 0;
  for (i=1; i<=4; i++) {
    sum += S[i];
  }
  printf("%.2f\n",(double)sum/4.0);
  return 0;
}