#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cstring>
#include <string>
#include <vector>
#include <queue>
#include <cmath>
#include <stack>
#include <set>
#include <map>
typedef long long ll;
typedef unsigned int uint;
using namespace std;

int main() {
	int n;
	cin >> n;
	double a[n];
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	double ans;

	if (n % 2) {
		ans = (a[n / 2] + a[n / 2 + 1]) / 2;
	} else {
		ans = a[n / 2];
	}
	cout << ans << endl;

}