using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using Number = System.Int64;
namespace Program
{
    public class Solver
    {

        public void Solve()
        {
            var n = sc.Integer();
            var k = sc.Integer();
            var u = sc.Long();
            var a = sc.Long(n - 1);
            Array.Sort(a);
            var ok = false;
            var l = 0; var r = n - 1;
            for (int _ = 0; _ < 20; _++)
            {
                var m = (l + r) / 2;
                var v = u + a[m];
                var s = new Set<long>();
                s.IsMultiSet = true;
                for (int i = n - 2; i >= 0; i--)
                    if (i != m) s.Add(a[i]);
                var cnt = 0;
                while (s.Count >= 2)
                {
                    var min = s[0];
                    s.RemoveAt(0);
                    var lb = s.UpperBound(v - min);
                    if (lb < s.Count)
                    {
                        cnt++;
                        s.RemoveAt(lb);
                    }
                }
                if (cnt < k) { ok = true; r = m; }
                else l = m;
            }
            if (!ok) IO.Printer.Out.WriteLine(-1);
            else IO.Printer.Out.WriteLine(a[r]);
        }
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
        static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex
{
    static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
    static public void Main()
    {
        var solver = new Program.Solver();
        solver.Solve();
        Program.IO.Printer.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer: StreamWriter
    {
        static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
        public static Printer Out { get; set; }
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
        public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
        public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
    }
    public class StreamScanner
    {
        public StreamScanner(Stream stream) { str = stream; }
        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) return 0;
            if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
            return buf[ptr++];
        }
        public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }

        public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n'; b = (char)read())
                if (b == 0) break;
                else if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long()
        {
            if (isEof) return long.MinValue;
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != 0 && b != '-' && (b < '0' || '9' < b));
            if (b == 0) return long.MinValue;
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
        public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
        private T[] enumerate<T>(int n, Func<T> f)
        {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f();
            return a;
        }

        public char[] Char(int n) { return enumerate(n, Char); }
        public string[] Scan(int n) { return enumerate(n, Scan); }
        public double[] Double(int n) { return enumerate(n, Double); }
        public int[] Integer(int n) { return enumerate(n, Integer); }
        public long[] Long(int n) { return enumerate(n, Long); }
    }
}
#endregion
#region Compair
static public class Pair
{
    static public Pair<FT, ST> Create<FT, ST>(FT f, ST s) where FT : IComparable<FT> where ST : IComparable<ST>
    {
        return new Pair<FT, ST>(f, s);
    }
    static public Pair<FT, ST> Min<FT, ST>(Pair<FT, ST> p, Pair<FT, ST> q) where FT : IComparable<FT> where ST : IComparable<ST>
    {
        return (p.CompareTo(q) <= 0) ? p : q;
    }
    static public Pair<FT, ST> Max<FT, ST>(Pair<FT, ST> p, Pair<FT, ST> q) where FT : IComparable<FT> where ST : IComparable<ST>
    {
        return (p.CompareTo(q) >= 0) ? p : q;
    }
}
public struct Pair<FT, ST>: IComparable<Pair<FT, ST>> where FT : IComparable<FT> where ST : IComparable<ST>
{
    public FT x;
    public ST y;
    public Pair(FT f, ST s) : this() { x = f; y = s; }

    public int CompareTo(Pair<FT, ST> other)
    {
        var cmp = x.CompareTo(other.x);
        return cmp != 0 ? cmp : y.CompareTo(other.y);
    }
    public override string ToString() { return string.Format("{0} {1}", x, y); }
}
#endregion
#region Set 
public class Set<T>: ICollection<T>
{
    public Set() { cmp = Comparer<T>.Default; }
    public Set(IComparer<T> comparer) { cmp = comparer; }
    public Set(Comparison<T> compare) { cmp = Comparer<T>.Create(compare); }
    AVLTree<Node> tree = new AVLTree<Node>();
    IComparer<T> cmp;

    /// <summary>
    /// 値の重複を許すならばtrue，そうでなければfalse
    /// </summary>
    public bool IsMultiSet { get; set; }
    /// <summary>
    /// コレクションのサイズ． O(1)
    /// </summary>
    public int Count { get { return tree.Count; } }

    /// <summary>
    /// 要素の追加．成功した場合true，そうでなければfalse．O(logN)
    /// </summary>
    public bool Add(T item)
    {
        var v = new Node() { Key = item };
        var lb = LowerBound(item);
        if (!IsMultiSet && UpperBound(item) != lb) return false;
        tree.Insert(v, lb);
        return true;
    }
    /// <summary>
    /// 要素の削除．成功した場合true，そうでなければfalse．O(logN)
    /// </summary>
    public bool Remove(T item)
    {
        var lb = LowerBound(item);
        var ub = UpperBound(item);
        if (ub == lb) return false;
        tree.RemoveAt(lb);
        return true;
    }
    /// <summary>
    /// 0-indexed で k 番目に小さい要素を削除．成功した場合true，そうでなければfalse．O(logN)
    /// </summary>
    public bool RemoveAt(int k)
    {
        if (k < 0 || k >= Count) return false;
        tree.RemoveAt(k);
        return true;
    }
    /// <summary>
    /// 0-indexed で k 番目に小さい要素を返す．O(logN)
    /// </summary>
    public T this[int index]
    {
        get
        {
            if (index < 0 || index >= Count) throw new IndexOutOfRangeException();
            var t = tree.Find(tree.root, index);
            return t.Key;
        }
    }
    /// <summary>
    /// 要素があるなら true，そうでなければfalse
    /// </summary>
    public bool Contains(T item) { return UpperBound(item) != LowerBound(item); }
    /// <summary>
    /// itemの値以上の要素の最小のインデックスを返す．O(logN)
    /// </summary>
    public int LowerBound(T item) { return tree.root.LowerBound(item, cmp); }
    /// <summary>
    /// itemの値より大きい要素の最小のインデックスを返す．O(logN)
    /// </summary>
    public int UpperBound(T item) { return tree.root.UpperBound(item, cmp); }
    /// <summary>
    /// O(N)でなめる
    /// </summary>
    public T[] Items
    {
        get
        {
            var ret = new T[Count];
            int ptr = 0;
            walk(tree.root, ret, ref ptr);
            return ret;
        }
    }

    public bool IsReadOnly { get { return false; } }

    void walk(Node root, T[] a, ref int ptr)
    {
        if (root.cnt == 0) return;
        walk(root.lst, a, ref ptr);
        a[ptr++] = root.Key;
        walk(root.rst, a, ref ptr);
    }

    void ICollection<T>.Add(T item) { Add(item); }
    public void Clear() { tree.root = tree.NIL; }
    public void CopyTo(T[] array, int arrayIndex) { ((ICollection<T>)Items).CopyTo(array, arrayIndex); }
    public IEnumerator<T> GetEnumerator() { return ((ICollection<T>)Items).GetEnumerator(); }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return ((ICollection<T>)Items).GetEnumerator(); }

    class Node: AVLTreeNode<Node>, IKey<T>
    {
        public T Key { get; set; }

        public override Node Push()
        {
            return this;
        }

    }
}

#endregion

#region AVLTree
public abstract class AVLTreeNode<T>: BinaryTreeNode<T>
    where T : AVLTreeNode<T>
{
    public int rank;
    public override void Update()
    {
        cnt = 1 + lst.cnt + rst.cnt;
        rank = 1 + Math.Max(lst.rank, rst.rank);
    }
}
public class AVLTree<T>: Tree<T>
    where T : AVLTreeNode<T>, new()
{
    protected override T insert(T t, T v, int k)
    {
        t = t.Push();
        if (t.cnt == 0)
        {
            v.cnt = 1;
            v.lst = NIL; v.rst = NIL;
            v.Update();
            return v;
        }
        if (t.lst.cnt >= k)
            t.lst = insert(t.lst, v, k);
        else
            t.rst = insert(t.rst, v, k - t.lst.cnt - 1);
        t.Update();

        return balance(t);
    }
    protected override T removeat(T t, int k)
    {
        t = t.Push();
        var cnt = t.lst.cnt;
        if (cnt < k) t.rst = removeat(t.rst, k - cnt - 1);
        else if (cnt > k) t.lst = removeat(t.lst, k);
        else
        {
            if (cnt == 0) return t.rst;
            if (t.rst.cnt == 0) return t.lst;

            var next = Find(t.lst, k - 1);
            var st = removeat(t.lst, k - 1);
            next.rst = t.rst;
            next.lst = st;
            t = next;
        }
        t.Update();
        return balance(t);
    }
    T balance(T t)
    {
        if (t.lst.rank - t.rst.rank == -2)
        {
            if (t.rst.lst.rank - t.rst.rst.rank > 0) t.rst = rotR(t.rst);
            t = rotL(t);
        }
        else if (t.lst.rank - t.rst.rank == 2)
        {
            if (t.lst.lst.rank - t.lst.rst.rank < 0) t.lst = rotL(t.lst);
            t = rotR(t);
        }
        return t;
    }
}
#endregion
#region BinaryTree
public interface IKey<K> { K Key { get; set; } }
public abstract class BinaryTreeNode<T>
    where T : BinaryTreeNode<T>
{

    public int cnt;
    public T lst, rst;
    public abstract T Push();
    /// <summary>
    /// 各ノードは必要に応じて Update を継承して使う
    /// </summary>
    public abstract void Update();
}

public abstract class Tree<TNode>
    where TNode : BinaryTreeNode<TNode>, new()
{
    public Tree() { NIL = new TNode(); NIL.lst = NIL; NIL.rst = NIL; root = NIL; }
    public readonly TNode NIL;
    public TNode root;
    public int Count { get { return root.cnt; } }
    protected TNode rotR(TNode t)
    {
        t = t.Push();
        var l = t.lst.Push();
        var lr = l.rst;
        l.rst = t;
        t.lst = lr;
        t.Update();
        l.Update();
        return l;
    }
    protected TNode rotL(TNode t)
    {
        t = t.Push();
        var r = t.rst.Push();
        var rl = r.lst;
        t.rst = rl;
        r.lst = t;
        t.Update();
        r.Update();
        return r;
    }
    public TNode Find(TNode t, int k)
    {
        t = t.Push();
        if (k == t.lst.cnt) return t;
        else if (k < t.lst.cnt) return Find(t.lst, k);
        else return Find(t.rst, k - t.lst.cnt - 1);
    }
    public void Insert(TNode v, int k) { root = insert(root, v, k); NIL.cnt = 0; }
    public void RemoveAt(int k) { root = removeat(root, k); NIL.cnt = 0; }
    protected abstract TNode insert(TNode t, TNode v, int k);
    protected abstract TNode removeat(TNode t, int k);
}
public static class TreeOperation
{
    static public int LowerBound<T, K>
          (this T t, K k, IComparer<K> cmp)
          where T : BinaryTreeNode<T>, IKey<K>
    {
        if (t.cnt == 0) return 0;
        if (cmp.Compare(k, t.Key) <= 0) return LowerBound(t.lst, k, cmp);
        else return 1 + t.lst.cnt + LowerBound(t.rst, k, cmp);
    }
    static public int UpperBound<T, K>
     (this T t, K k, IComparer<K> cmp)
       where T : BinaryTreeNode<T>, IKey<K>
    {
        if (t.cnt == 0) return 0;
        if (cmp.Compare(t.Key, k) <= 0) return 1 + t.lst.cnt + UpperBound(t.rst, k, cmp);
        else return UpperBound(t.lst, k, cmp);
    }
}

#endregion
#region Set<T>
public class aSet<T>
    where T : IComparable<T>
{

    Node root = Node.NIL;

    public int Count { get { return root.cnt; } }
    public void Add(T v) { Insert(v, LowerBound(v)); }
    public bool Remove(T v)
    {
        if (EqualRange(v) == 0) return false;
        RemoveAt(LowerBound(v));
        return true;
    }
    #region Impl
    public void Insert(T v, int k)
    {
        root = insert(root, v, k);
    }
    public void RemoveAt(int k)
    {
        root = removeat(root, k);
    }
    public int EqualRange(T v) { return UpperBound(v) - LowerBound(v); }
    public int LowerBound(T v) { return lowerBound(root, v); }
    public int UpperBound(T v) { return upperBound(root, v); }
    public T this[int k] { get { return find(root, k); } }
    Node insert(Node t, T v, int k)
    {
        Debug.Assert(t.cnt >= k);
        if (t == Node.NIL) return new Node(v);
        if (t.lst.cnt >= k)
            t.lst = insert(t.lst, v, k);
        else
            t.rst = insert(t.rst, v, k - t.lst.cnt - 1);
        t.Update();

        if (t.lst.h - t.rst.h == -2)
        {
            if (t.rst.lst.h - t.rst.rst.h > 0) t.rst = rotR(t.rst);
            t = rotL(t);
        }
        else if (t.lst.h - t.rst.h == 2)
        {
            if (t.lst.lst.h - t.lst.rst.h < 0) t.lst = rotL(t.lst);
            t = rotR(t);
        }
        t.Update();
        return t;
    }
    Node removeat(Node t, int k)
    {
        Debug.Assert(t.cnt > k);
        var cnt = t.lst.cnt;
        if (cnt < k) t.rst = removeat(t.rst, k - cnt - 1);
        else if (cnt > k) t.lst = removeat(t.lst, k);
        else
        {
            if (cnt == 0) return t.rst;
            if (t.rst.cnt == 0) return t.lst;

            t.val = find(t, k - 1);
            t.lst = removeat(t.lst, k - 1);
        }
        t.Update();
        if (t.lst.h - t.rst.h == -2)
        {
            if (t.rst.lst.h - t.rst.rst.h > 0) t.rst = rotR(t.rst);
            t = rotL(t);
        }
        else if (t.lst.h - t.rst.h == 2)
        {
            if (t.lst.lst.h - t.lst.rst.h < 0) t.lst = rotL(t.lst);
            t = rotR(t);
        }
        else t.Update();
        return t;
    }

    int lowerBound(Node t, T v)
    {
        if (t.cnt == 0) return 0;
        if (v.CompareTo(t.val) <= 0) return lowerBound(t.lst, v);
        else return t.lst.cnt + 1 + lowerBound(t.rst, v);
    }
    int upperBound(Node t, T v)
    {
        if (t.cnt == 0) return 0;
        if (t.val.CompareTo(v) <= 0) return t.lst.cnt + 1 + upperBound(t.rst, v);
        else return upperBound(t.lst, v);
    }
    T find(Node t, int k)
    {
        Debug.Assert(k < t.cnt);
        if (k == t.lst.cnt) return t.val;
        else if (k < t.lst.cnt) return find(t.lst, k);
        else return find(t.rst, k - (t.lst.cnt + 1));
    }
    Node rotR(Node t)
    {
        var l = t.lst;
        var lr = l.rst;
        l.rst = t;
        t.lst = lr;
        t.Update();
        l.Update();
        return l;
    }
    Node rotL(Node t)
    {
        var r = t.rst;
        var rl = r.lst;
        t.rst = rl;
        r.lst = t;
        t.Update();
        r.Update();
        return r;
    }
    #endregion
    class Node
    {
        static public readonly Node NIL = new Node();
        public int h;
        public int cnt;
        internal T val;
        internal Node lst, rst;
        private Node() { }
        internal Node(T v) { h = 1; cnt = 1; val = v; lst = NIL; rst = NIL; }
        public void Update()
        {
            if (cnt == 0) return;
            h = 1 + Math.Max(lst.h, rst.h);
            cnt = 1 + lst.cnt + rst.cnt;
        }
        public override string ToString()
        {
            return string.Format("count:{0}, value:{1}", cnt, val);
        }
        public T[] Items { get { return items(this); } }
        static public T[] items(Node t)
        {
            var ret = new T[t.cnt];
            var ptr = 0;
            dfs(t, ref ptr, ret);
            return ret;
        }
        static void dfs(Node t, ref int ptr, T[] ret)
        {
            if (t == Node.NIL) return;
            dfs(t.lst, ref ptr, ret);
            ret[ptr++] = t.val;
            dfs(t.rst, ref ptr, ret);
        }
    }
    public T[] Items { get { return root.Items; } }
    public override string ToString() { return string.Format("Count = {0}", Count); }

}
#endregion