/* This is an answer to sf25.txt. */

#include <stdio.h>

int main(void)
{
  double x[10000];
  int xlen = 0;
  int i;
  int j;

  while ((xlen < 10000) && (scanf("%lf",&x[xlen]) == 1)) ++xlen;

  while (xlen > 2) {
    i = 0;
    for (j = 1;j < xlen;++j) if (x[j] < x[i]) i = j;
    x[i] = x[--xlen]; /* discard the smallest */
    i = 0;
    for (j = 1;j < xlen;++j) if (x[j] > x[i]) i = j;
    x[i] = x[--xlen]; /* discard the largest */
  }

  if (xlen == 1) printf("%.999g\n",x[0]);
  if (xlen == 2) printf("%.999g\n",(x[0] + x[1]) / 2);
  return 0;
}