#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
//#define int long long
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
using namespace std;
typedef pair<int,int> pii;
typedef pair<pii,int> ipii;
const int INF = 1e9+10;
const int MAXN = 2e3+10;
int n, p, q;
vector <int> a;
int dp[MAXN][MAXN];
bool cek(int x){ // lengthnya x
for(int j=0; j<=n; j++) dp[0][j] = 0;
for(int i=1; i<=n; i++){
for(int j=0; j<=n; j++) dp[i][j] = INF;
}
for(int i=1; i<=n; i++){ // mau kenain a[i]
// a[i]-x+1 -- a[i]
auto it1 = lower_bound(a.begin(), a.end(), a[i]-x+1); // small
int idx = -1;
if(it1 == a.begin()) idx = 0; // bisa karena negatif
else {
it1--; // ambil belakangnya
idx = (it1-a.begin());
}
//cout << i << ' ' <<a[i]<< ' ' << idx << " p\n";
auto it2 = lower_bound(a.begin(), a.end(), a[i]-2*x+1); // big
int idx2 = -1;
if(it2 == a.begin()) idx2 = 0;
else {
it2--; // ambil belakangnya
idx2 = (it2-a.begin());
}
//cout << i << ' ' <<a[i]<< ' ' << idx2 << " p\n";
for(int j=0; j<=min(i, q); j++){ // num big camera
dp[i][j] = min(dp[i][j], dp[idx][j]+1); //small
if(j!=0)
dp[i][j] = min(dp[i][j], dp[idx2][j-1]); //big
//cout << i << ' ' << j << ' ' << dp[i][j] << '\n';
}
}
int mn = INF;
for(int i=0; i<=q; i++) mn = min(mn, dp[n][i]);
return (mn <= p); // pake q big, harus <= small
}
void bin(){
int l=1, r=INF, mid=0, cnt=-1;
while(l<=r){
mid = md;
if(cek(md)){
r = mid-1; cnt = mid;
} else l = mid+1;
}
cout << cnt << '\n';
}
signed main(){
cin >> n >> p >> q; // small - big
q = min(q, n);
a.pb(0);
for(int i=1; i<=n; i++){
int x; cin >> x;
a.pb(x);
}
sort(a.begin(), a.end());
bin();
//cout << cek(1) << " p\n";
}
