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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		int ret = inf;
		for(int i=0;i<N;i++){
			ret = Math.Min(ret, calc(i));
		}
		Console.WriteLine(ret);
		
	}
	const int inf = (int) 1e9;
	int calc(int midx){
		
		List<int> candi = new List<int>();
		List<int> compo = new List<int>();
		int min = A[midx];
		for(int i=0;i<N;i++){
			if(A[i] < min){
				compo.Sort();
				compo.Reverse();
				while(compo.Count >= K){
					candi.Add(compo[compo.Count - 1]);
					compo.RemoveAt(compo.Count - 1);
				}
				compo = new List<int>();
			} else {
				compo.Add(A[i]);
			}
		}
		if(compo.Count >= K){
			compo.Sort();
			compo.Reverse();
			while(compo.Count >= K){
				candi.Add(compo[compo.Count - 1]);
				compo.RemoveAt(compo.Count - 1);
			}
		}
		
		if(candi.Count < Q) return inf;
		candi.Sort();
		return candi[Q-1] - min;
		
	}
	
	
	
	
	int N, K, Q;
	int[] A;
	public Sol(){
		var d = ria();
		N = d[0]; K = d[1]; Q = d[2];
		A = ria();
	}

	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(char sep=' '){return Console.ReadLine().Split(sep);}
	static int[] ria(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>int.Parse(e));}
	static long[] rla(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>long.Parse(e));}
	static double[] rda(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>double.Parse(e));}
}