#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)



int N, M, A[101010];
//-----------------------------------------------------------------------------------
bool chk(int idx) {
    int P = A[0] + A[idx];
    int cnt = 0;
    int L = 1, R = N - 1;
    while (L < R) {
        if (L == idx) L++;
        else if (R == idx) R--;
        else if (A[L] + A[R] <= P) L++;
        else {
            cnt++;
            L++; R--;
        }
    }

    return cnt < M;
}
//-----------------------------------------------------------------------------------
int main() {
    cin >> N >> M;
    rep(i, 0, N) scanf("%d", &A[i]);
    A[N] = -1;

    sort(A + 1, A + N);

    int lo = 0, hi = N;
    while (lo + 1 != hi) {
        int md = (lo + hi) / 2;
        if (chk(md)) hi = md;
        else lo = md;
    }

    printf("%d\n", A[hi]);
}