#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define pa pair<ll, ll>
#define fi first
#define se second
#define bit(mask, j) ((mask >> j) & 1)
#define t_test int t;cin >> t;while(t--)
const ll mod = 1e9 + 7;
const ll INF = 1e18;
inline void adm(ll &x){if(x>=mod)x%=mod;else if(x<0)x+=mod;}
//--------------------------------------------------------------------
ll n, p, q;
const ll N = 2003;
ll a[N];
ll pos_p[N], pos_q[N], dp[N][N];
bool check(ll w) {
FOR(i, 1, n) {
ll sum = 1;
FORD(j, i, 1) {
if(sum <= w) {
pos_p[i] = j;
}
if(sum <= 2 * w) {
pos_q[i] = j;
}
sum += a[j] - a[j - 1];
}
}
memset(dp, -1, sizeof dp);
dp[0][0] = q;
FOR(i, 1, n) {
FOR(j, 0, p) {
ll u = pos_p[i], v = pos_q[i];
if(j - 1 >= 0) dp[i][j] = dp[u - 1][j - 1];
dp[i][j] = max(dp[i][j], dp[v - 1][j] - 1);
}
}
FOR(i, 0, p) {
if(dp[n][i] >= 0) return true;
}
return false;
}
void hbmt() {
cin >> n >> p >> q;
p = min(n, p);
FOR(i, 1, n) {
cin >> a[i];
}
sort(a + 1, a + n + 1);
ll l = 1, r = a[n], w = -1;
while(l <= r) {
ll mid = l + r >> 1;
if(check(mid)) {
r = mid - 1;
w = mid;
}
else l = mid + 1;
}
cout << w;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
if(fopen("hbmt.inp", "r")) {
freopen("hbmt.inp", "r", stdin);
freopen("hbmt.out", "w", stdout);
}
// t_test
hbmt();
return 0;
}
