`

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <vector>
#include <utility>
#include <cmath>
#include <iomanip>
#include <string>
#include <cstring>
#include <unordered_set>
#include <unordered_map>
#include <map>
#include <queue>
#include <set>
const int maxn = 10010;
using namespace std;

int n, m;
int a[100010];
bool check(int val)     //判断>=差值val的个数是否大于一半
{
	int cnt = 0, k = 0;
	for (int i = 0; i < n; i++)
	{
		while (k < n && a[k] - a[i] < val)
		{
			k++;
		}
		cnt += n - k;
	}
	return cnt > m;
}
int main() {
	cin >> n;
	m = n * (n - 1) / 4;            //差值的个数 C(n,2)
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}
	sort(a, a + n);
	int l = 0, r = a[n - 1] - a[0], mid;         //r为最大差值
	while (l <= r)
	{
		mid = l + (r - l) / 2;
		if (check(mid))          // 大于一半往右找
			l = mid + 1;
		else                     // 否则往左找
			r = mid - 1;
	}
	int ans = l - 1;                // 跳出while时 ， l = r + 1；
	cout << ans << endl;
	return 0;
}