#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define int long long
//using namespace __gnu_pbds;
using namespace std;
const int mod = 998244353;
const int inf = 1e18;
const int maxx = 5e5 + 5;
const int lg = 26;
//typedef tree <int, null_type, less_equal <int>, rb_tree_tag, tree_order_statistics_node_update> ordered_multiset;
bool c (int w, vector <int>& a, int p, int q) {
int i = 0, n = a.size();
while (i < n && q > 0) {
int end = a[i] + 2 * w;
while (i < n && a[i] <= end) {
i++;
}
q--;
}
while (i < n && p > 0) {
int end = a[i] + w;
while (i < n && a[i] <= end) {
i++;
}
p--;
}
return i == n;
}
void solve () {
int n, p, q, l = 1, r, ans;
cin >> n >> p >> q;
vector <int> a(n);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
sort(a.begin(), a.end());
r = ans = a.back() - a.front() + 1;
while (l <= r) {
int m = l + (r - l) / 2;
if (c(m, a, p, q)) {
ans = m;
r = m - 1;
}
else {
l = m + 1;
}
}
cout << ans - 1 << endl;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) {
solve();
}
}
