#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>
using namespace std;

typedef long long ll;
typedef pair<int, int> P;
const int INF = (int)1e9 + 1;

int n, m, a[100010];

bool check(int x) {
	int p = a[0] + a[x];
	int cnt = 0;
	int L = 1, R = n - 1;
	while (L < R) {
		if (L == x || a[L] + a[R] <= p) {
			L++;
		}
		else if (R == x) {
			R--;
		}
		else {
			cnt++;
			L++;
			R--;
		}
	}

	return cnt < m;
}

int main(void) {
	cin >> n >> m;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	a[n] = -1;

	sort(a + 1, a + n);

	int low = 0, high = n;
	while (low + 1 != high) {
		int mid = (low + high) / 2;
		if (check(mid)) {
			high = mid;
		}
		else {
			low = mid;
		}
	}
	cout << a[high] << endl;
}