#include <bits/stdc++.h>
#define int long long
#define f first
#define s second
#define pb push_back
#define endl '\n'
using namespace std;
int N,K,B,a[2005];
bool check(int x) {
priority_queue<pair<int, pair<int, int>>> p;
p.push({1, {K, B}});
while (!p.empty()) {
auto cur = p.top();
p.pop();
int idx = cur.f;
int ku = cur.s.f;
int bu = cur.s.s;
// cout << idx << ' ' << ku << ' ' << bu << endl;
if (idx >= N + 1) return true;
int nxt_idx = idx;
if (ku > 0) {
while (a[nxt_idx + 1] - a[idx] + 1 <= x && nxt_idx <= N) nxt_idx++;
p.push({nxt_idx + 1, {ku - 1, bu}});
}
nxt_idx = idx;
if (bu > 0) {
while (a[nxt_idx + 1] - a[idx] + 1 <= 2 * x && nxt_idx <= N) nxt_idx++;
p.push({nxt_idx + 1, {ku, bu - 1}});
}
}
return false;
}
void solve() {
cin >> N >> K >> B;
for (int i = 1; i <= N; i++) cin >> a[i];
sort(a + 1, a + 1 + N);
int l = 1;
int r = 1e9;
int ans = -1;
while (l <= r) {
int mid = (l + r) / 2;
if (check(mid)) {
ans = mid;
r = mid - 1;
}
else l = mid + 1;
} cout << ans << endl;
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int tttt = 1;
// cin >> tttt;
while (tttt--) solve();
}
