#include<stdio.h>
int main(void) {
    int N;
    int a[50];
    int length = sizeof(a) / sizeof(int);
    int step, i, j;
    for(step = length / 2; step > 0; step /= 2) {
        for(i = step; i < length; i++){
            int tmp = a[i];
            int j = i;
            for(j = i; j >= step; j -= step) {
                if(a[j-step] > tmp) {
                    a[j] = a[j-step];
                } else {
                    break;
                }
            }
            a[j] = tmp;
        }
    
    float sum = (a[0] + a[1]) / 2;
    if(N = 2) {
      printf("%f", sum);
    } else {
      for(int i = 2; i < N -1; i++) {
        sum = (int)(sum + a[i]) / 2;
      }
      printf("%f", sum);
    }