#include <bits/stdc++.h>
using namespace std;
using ll = long long;
vector<int> a;
int n, A, B;
bool ok(int m) {
	queue<int> q;
	q.push(-1);
	int i = A - 1;
	while (i < n && q.size()) {
		if (i - q.front() < A) {
			i++;
		} else {
			if (i - q.front() > B || a[i] - a[q.front() + 1] > m) {
				q.pop();
			} else {
				q.push(i);
				i++;
			}
		}
	}
	while (q.size() > 1) q.pop();
	return (q.size() && q.front() == n - 1);
}
int main() {
	cin >> n >> A >> B;
	a = vector<int>(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	sort(begin(a), end(a));
	int l = 0, r = a[n - 1];
	// int c = 0;
	while (r - l > 0) {
		int m = (l + r) / 2;
		// cout << l << " " << r << endl;
		if (ok(m)) {
			r = m;
		} else {
			l = m + 1;
		}
	}
	cout << r << endl;
}
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