/*
* #include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
const int N_max = 1000005;
int n, A, B;
vector<int> v;
int dp[N_max];
void reading(){
cin >> n >> A >> B;
v.resize(n + 1);
for(int i = 1; i <= n; i++) {
cin >> v[i];
dp[i] = -1;
}
sort(v.begin() + 1, v.end());
}
int main() {
reading();
for(int i = 0; i <= n - A; i++) {
if (dp[i + A] == -1)
dp[i + A] = max(v[i + A] - v[i + 1], dp[i]);
else
dp[i + A] = min(dp[i + A], max(v[i + A] - v[i + 1], dp[i]));
for (int j = A + 1; j <= B && i + j <= n; j++)
if(dp[i + j] == -1)
dp[i + j] = max(v[i + j] - v[i + 1], dp[i]);
else
dp[i + j] = min(dp[i + j], max(v[i + j] - v[i + 1], dp[i]));
cout << i << " " << dp[i] << endl;
}
cout << dp[n];
}
*/
#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
using namespace std;
const int N_max = 1000005;
ifstream fin("a.in");
int n, A, B;
vector<int> v;
int dp[N_max];
void reading(){
cin >> n >> A >> B;
v.resize(n + 1);
for(int i = 1; i <= n; i++) {
cin >> v[i];
dp[i] = -1;
}
sort(v.begin() + 1, v.end());
}
int main() {
reading();
for(int i = A; i <= n; i++){
for(int j = A; j <= B && i >= j; j++)
if(dp[i - j] != -1){
if(dp[i] == -1)
dp[i] = max(dp[i - j], v[i] - v[i - j + 1]);
else
dp[i] = min(dp[i], max(dp[i - j], v[i] - v[i - j + 1]));
}
}
cout << dp[n];
}
