#include <bits/stdc++.h>
#define nl "\n"
#define no "NO"
#define yes "YES"
#define fi first
#define se second
#define vec vector
#define task "main"
#define _mp make_pair
#define ii pair<int, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
#define unq(x) sort(all(x)); x.resize(unique(all(x)) - x.begin())
using namespace std;
template<typename U, typename V> bool maxi(U &a, V b) {
if (a < b) { a = b; return 1; } return 0;
}
template<typename U, typename V> bool mini(U &a, V b) {
if (a > b || a == -1) { a = b; return 1; } return 0;
}
const int N = (int)2e3 + 9;
const int mod = (int)1e9 + 7;
void prepare(); void main_code();
int main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
const bool MULTITEST = 0; prepare();
int num_test = 1; if (MULTITEST) cin >> num_test;
while (num_test--) { main_code(); }
}
void prepare() {};
int dp[N][N], a[N], nxt1[N], nxt2[N];
void main_code() {
int n, p, q; cin >> n >> p >> q;
for(int i = 1; i <= n; ++i) cin >> a[i];
sort(a + 1, a + n + 1);
if (p + q >= n) evoid(1);
// binary search w
// dp[i][j] => min k have used so that cover first i point
// j : number of small camera used
int l = 1, r = (int)1e9 + 100, ans = -1;
while (l <= r) {
int m = (l + r) >> 1, w = m;
memset(dp, -1, sizeof dp); dp[0][0] = 0;
int j = 0; FOR(i, 1, n) {
while (j + 1 <= n and a[j + 1] - a[i] + 1 <= w) ++j;
nxt1[i] = j;
}
j = 0; FOR(i, 1, n) {
while (j + 1 <= n and (a[j + 1] - a[i] + 2) / 2 <= w) ++j;
nxt2[i] = j;
}
FOR(i, 0, n - 1) FOR(j, 0, p) if (dp[i][j] != -1) {
if (j + 1 <= p)
mini(dp[nxt1[i + 1]][j + 1], dp[i][j]);
mini(dp[nxt2[i + 1]][j], dp[i][j] + 1);
}
bool ok = 0;
FOR(j, 0, p) if (dp[n][j] != -1 and dp[n][j] <= q) {
ok = 1; break ;
}
if (ok) {
ans = m; r = m - 1;
} else
l = m + 1;
}
cout << ans;
}
/* Let the river flows naturally */
