include <iostream>
using namespace std;
int main(void){
    // Your code here!
    int n,tmp;
    double ans=0;
    cin>>n;
    double num[n];
    for(int k=0;k<n;k++){
        cin>>num[k];
    }
        for (int i=0; i<n; ++i) {
            for (int j=i+1; j<n; ++j) {
                if (num[i] > num[j]) {
                    tmp =  num[i];
                    num[i] = num[j];
                    num[j] = tmp;
      }
    }
  }
  ans=num[0];
  for(int i=0;i<n-1;i++){
      ans=(ans+num[i+1])/2;
  }
  /*for(int i=0;i<n;i++){
      cout<<i;
      cout<<num[i]<<endl;
  }*/
  cout<<ans;
  return 0;
}