1620

#include <iostream>
//#include <chrono>
//#include <fstream>
//#include <bits/stdc++.h>
#include <vector>
#include <algorithm>
#include <climits>

#define mp make_pair
#define pb push_back
#define eb emplace_back
#define f first
#define s second
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;

int n, n_team, team_size;
vector<int> vec;

bool check(int a) {
    int st = 0, fn = 0;
    int count = 0;
    while (fn < n) {
        if (fn - st + 1 >= team_size) {
            count++;
            st = fn = fn + 1;
            continue;
        }
        if (vec[fn + 1] - vec[st] <= a) {
            fn++;
        }
        else
            st++;
    }
    return count >= n_team;
}

int main() {
    /*ifstream cin("in.txt");
    ofstream cout("out.txt");
    auto start_time = chrono::high_resolution_clock::now();*/

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);


    cin >> n >> n_team >> team_size;
    vec.assign(n, 0);
    for (int i = 0; i < n; i++) cin >> vec[i];
    sort(all(vec));
    vec.push_back(INT_MAX);
    int l = -1, r = vec[n - 1] - vec[0] + 1;
    while (l + 1 < r) {
        int mid = (l + r) / 2;
        if (check(mid))
            r = mid;
        else
            l = mid;
    }
    cout << r << endl;

    /*auto end_time = chrono::high_resolution_clock::now();
    chrono::duration<double> duration = end_time - start_time;
    cout << duration.count() << "\n";
    cin.close();
    cout.close();*/
    return 0;
}