#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 100010;
int n, m;
int a[N];
bool check(int mid)
{
	int t = a[mid] + a[1] + 1, res = 0, tt = n;
	for (int i = 2; i <= tt; i ++ )
	{
		if (i == mid) continue;
		if (tt == mid) tt -- ;
		if (a[i] + a[tt] >= t) res ++ , tt -- ;
	}
	return res < m;
}
signed main()
{
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n >> m;
	a[n + 1] = -1;
	for (int i = 1; i <= n; i ++ )
		cin >> a[i];
	sort(a + 2, a + n + 1);
	int l = 2, r = n, res = n + 1;
	while (l <= r)
	{
		int mid = l + r >> 1;
		if (check(mid)) r = mid - 1, res = mid;
		else l = mid + 1;
	}
	cout << a[res];
	return 0;
}