Problem:
Score : 600 points

Problem Statement

You are given an integer sequence A of length N and an integer K.
You will perform the following operation on this sequence Q times:

Choose a contiguous subsequence of length K, then remove the smallest element among the K elements contained in the chosen subsequence (if there are multiple such elements, choose one of them as you like).

Let X and Y be the values of the largest and smallest element removed in the Q operations. You would like X-Y to be as small as possible.
Find the smallest possible value of X-Y when the Q operations are performed optimally.

Constraints

1 \leq N \leq 2000

1 \leq K \leq N

1 \leq Q \leq N-K+1

1 \leq A_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K Q
A_1 A_2 ... A_N

Output

Print the smallest possible value of X-Y.

Sample Input 1

5 3 2
4 3 1 5 2

Sample Output 1

1

In the first operation, whichever contiguous subsequence of length 3 we choose, the minimum element in it is 1.
Thus, the first operation removes A_3=1 and now we have A=(4,3,5,2).
In the second operation, it is optimal to choose (A_2,A_3,A_4)=(3,5,2) as the contiguous subsequence of length 3 and remove A_4=2.
In this case, the largest element removed is 2, and the smallest is 1, so their difference is 2-1=1.

Sample Input 2

10 1 6
1 1 2 3 5 8 13 21 34 55

Sample Output 2

7

Sample Input 3

11 7 5
24979445 861648772 623690081 433933447 476190629 262703497 211047202 971407775 628894325 731963982 822804784

Sample Output 3

451211184

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

/**
 * Created by darshan on 5/30/19.
 */
public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;

        st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int k = Integer.parseInt(st.nextToken());
        int q = Integer.parseInt(st.nextToken());
        int[] num = new int[n];
        st = new StringTokenizer(br.readLine());
        for (int i = 0; i < n; i++) {
            num[i] = Integer.parseInt(st.nextToken());
        }

        int minDiff = Integer.MAX_VALUE;
        PriorityQueue<Integer> currentSubsequence = new PriorityQueue<>();
        PriorityQueue<Integer> leastQElements = new PriorityQueue<>((o1, o2) -> o2 - o1);
        for (int i = 0; i < n; i++) {
            int low = num[i];
            currentSubsequence.clear();
            leastQElements.clear();
            for (int j = 0; j <= n; j++) {
                if (j == n || num[j] < low) {
                    while (currentSubsequence.size() - k + 1 > 0) {
                        leastQElements.add(currentSubsequence.poll());
                    }
                } else {
                    currentSubsequence.add(num[j]);
                }
            }
            while (leastQElements.size() > q) {
                leastQElements.poll();
            }
            if (leastQElements.size() == q) {
                minDiff = Math.min(minDiff, leastQElements.poll() - low);
            }
        }
        System.out.println(minDiff);
    }
}