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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
#define F first
//#define S second
#define dq deque
#define vc vector
#define INF (0x3f3f3f3f)
#define LINF ((long long)(0x3f3f3f3f3f3f3f3f))
#define Pb push_back
#define Mp make_pair
#define ll long long
#define _tp template
#define _tyn typename
#define Pf push_front
#define itor iterator
#define sint short int
#define ull unsigned ll
#define pii pair<int,int>
#define uint unsigned int
#define All(x) x.begin(),x.end()
#define B cout << "BreakPoint" << endl;
#define Fin(a) freopen(a,"r",stdin)
#define Fout(a) freopen(a,"w",stdout)
#define Ms(_data) memset(_data,0,sizeof(_data))
#define Msn(_data,_num) memset(_data,_num,sizeof(_data))
#define Fastio ios_base::sync_with_stdio(false);cin.tie(0);
#define O_(x) cout << #x << " " << x << "  ";
#define O(x) cout << #x << " " << x << endl;
using namespace std;
#define Mymax(a,b) if(a<b) a = b
#define Mymin(a,b) if(a>b) a = b
void Print(int _x){printf("%d\n",_x);}
void Print(ll _x){printf("%lld\n",_x);}
_tp<_tyn T>void Print( T _a[] , int _s , int _t ){
    for( int i = _s ; i <= _t ; i++ )
        cout << _a[i] << " ";
   	cout << endl;
}
#define il inline
#define rg register
struct InputReader{
    static const int bs = 100000;
    char buf[bs];
    int p;
    il InputReader():p(bs) {}
    il void Flush(){
        p = 0;
        fread(buf, 1, bs, stdin);
    }
    il char C(){
        if(p >= bs) Flush();
        return buf[p++];
    }
    int Getnum(){
        char ch = C();
        while( ch < '0'  ||  ch > '9' ) ch = C();
        return (int)(ch-'0');
    }
    il int operator() (){
        int ans = 0;
        char ch = C();
        int fu = 1;
        while( ch < '0'  ||  ch > '9' ){
            if( ch == '-' ) fu = -1;
            ch = C();
        }
        while( ch >= '0'  &&  ch <= '9' ){
            ans *= 10;
            ans += ch-'0';
            ch = C();
        }
        return ans * fu;
    }
    ll Readll(){
        ll ans = 0LL;
        ll fu = 1;
        char ch = C();
        while( ch < '0'  ||  ch > '9' ){
            if( ch == '-' ) fu = -1;
            ch = C();
        }
        while( ch >= '0'  &&  ch <= '9' ){
            ans *= 10LL;
            ans += ch-'0';
            ch = C();
        }
        return ans * fu;
    }
    il void Readstring( string &x ){
        x.clear();
        char ch = C();
        while( !isdigit(ch)  &&  !isalpha(ch) ) ch = C();
        while( isdigit(ch)  ||  isalpha(ch) ){
            x += ch;
            ch = C();
        }
    }
    il int Readchstr( char c[] ){
        int p = 0;
        char ch = C();
        while( !isdigit(ch)  &&  !isalpha(ch) ) ch = C();
        while( isdigit(ch)  ||  isalpha(ch) ){
            c[p] = ch;
            ch = C();
            p++;
        }
        c[p] = '\0';
        return p;
    }
    il void Readalpha( char &c ){
        c = C();
        while( !isalpha(c) ) c = C();
    }
    il void Specialread( char &c ){
        c = C();
        while( c != 'o'  &&  c != 'x'  &&  c != '?' ) c = C();
    }
}In;
il void Read( int &x ){ x = In(); }
il void Read( int &x, int &y ){ x = In(); y = In(); }
il void Read( int &x1 , int &x2 , int &x3 ){
    x1 = In(); x2 = In(); x3 = In();
}
il void Read( int &x1 , int &x2 , int &x3 , int &x4 ){
    x1 = In(); x2 = In(); x3 = In(); x4 = In();
}
il void Read( ll &x ){ x = In.Readll(); }
il void Read( ll &x, ll &y ){ x = In.Readll(); y = In.Readll(); }
il void Read( ll &x1 , ll &x2 , ll &x3 ){
    x1 = In.Readll(); x2 = In.Readll(); x3 = In.Readll();
}
il void Read( ll &x1 , ll &x2 , ll &x3 , ll &x4 ){
    x1 = In.Readll(); x2 = In.Readll(); x3 = In.Readll(); x4 = In.Readll();
}
clock_t _starttime , _endtime;
il void FILEIO(){
    #ifdef InterestingLSY
        _starttime = clock();
        Fin("in.in");
    #endif
}
#ifdef InterestingLSY
    #include <windows.h>
    #include <psapi.h>
#endif
il void END(){
    #ifdef InterestingLSY
        _endtime = clock();
        double _timeuse = (_endtime-_starttime)* 1000.0 / CLOCKS_PER_SEC;
        printf("\n\nTime usage:\n%.0lf ms\n",_timeuse);
        HANDLE _handle = GetCurrentProcess();
        PROCESS_MEMORY_COUNTERS pmc;
        GetProcessMemoryInfo(_handle,&pmc,sizeof(pmc));
        double _memuse = pmc.PeakPagefileUsage/1024.00/1024.00;
        printf("Memory usage:\n%.1lf MB\n\n",_memuse);
    #endif
    exit(0);
}
#define For(i,j) for( rg int (i) = 1 ; (i) <= (j) ; (i)++ )
#define For0(i,j) for( rg int (i) = 0 ; (i) < (j) ; (i)++ )
#define Forx(i,j,k) for( rg int (i) = (j) ; (i) <= (k) ; (i)++ )
#define Forstep(i,j,k,st) for( rg int (i) = (j) ; (i) <= (k) ; (i) += (st) )
#define fOR(i,j) for( rg int (i) = (j) ; (i) >= 1 ; (i)-- )
#define fOR0(i,j) for( rg int (i) = (j)-1 ; (i) >= 0 ; (i)-- )
#define fORx(i,j,k) for( rg int (i) = (k) ; (i) >= (j) ; (i)-- )
int dx[] = {0,-1,0,1};
int dy[] = {1,0,-1,0};
//			D L U  R
#define Mymod(a,b) if( a >= b ) a -= b;
#define Rmod(a,b) a = (a%b+b)%b
/////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////
#define MAXN 2010

int n,k,q;
int a[MAXN];

bool cannot[MAXN];
int st;
vc<int> v;

int main(){
	FILEIO();

	Read(n,k,q);
	For(i,n)
		Read(a[i]);

	int ans = INF;
	For(i,n){
		Ms(cannot);
		v.clear();
		st = a[i];
		For(j,n)
			if( a[j] < st ){
				Forx(l,max(j-k+1,1),min(j+k-1,n))
					cannot[l] = 1;
			}
		if(cannot[i]) continue;
		For(j,n)
			if(!cannot[j])
				v.Pb(a[j]);
		if( v.size() < q ) continue;
		sort(All(v));
		Mymin(ans,v[q-1]-st);
	}

	printf("%d\n",ans);

	END();
}