#include<cstdio>
#include<vector>
#include<algorithm>


using namespace std;


int n, m, k;
vector<int> a;


void min_u(int& d, int v)
{
	if(d<0 || d>v) d=v;
}


int solve_x(int i)
{
	int score, min_score;
	int s, e;

	score=k+a[i];
	s=0;
	e=2*m-1;
	if(i<=2*m-1) e++;

	min_score=-1;
	for(;s<e;s++,e--)
	{
		if(s==i) s++;
		if(e==i) e--;
		min_u(min_score, a[s]+a[e]);
	}

	if(min_score>score) return 0;
	return 1;
}


int solve(void)
{
	int s, e, c;
	int partner=-1;

	s=0;
	e=a.size()-1;
	for(;s<=e;)
	{
		c=(s+e)/2;
		if(solve_x(c))
		{
			min_u(partner, a[c]);
			s=c+1;
		}
		else
		{
			e=c-1;
		}
	}
	return partner;
}


int main(void)
{
	while(scanf("%d%d", &n, &m)==2)
	{
		scanf("%d", &k);
		a.resize(n-1);
		for(int i=0;i<n-1;i++)
		{
			scanf("%d", &a[i]);
		}
		sort(a.begin(), a.end(), greater<int>());

		printf("%d\n", solve());
	}

	return 0;
}