/* 29 . 03 . 2008 */
#include <bits/stdc++.h>
using namespace std ;
typedef long long ll ;
typedef vector<int> vi ;
typedef vector<pair<int,int>> vii ;
typedef pair<int,int> pii ;
typedef pair<ll,int> pli ;
typedef pair<int,ll> pil ;
typedef pair<ll,ll> pll ;
#define FOR(i,a,b) for(int i(a) ; i <= (int)b ; i++)
#define FORD(i,a,b) for(int i(a) ; i >= (int)b ; i--)
#define FORN(i,a,b) for(int i(a) ; i < (int)b ; i++)
#define all(a) a.begin() , a.end()
#define pb push_back
#define fi first
#define se second
#define endl '\n'
#define BIT(mask,i) ((mask>>i)&1)
#define builtin_popcount builtin_popcountll
#define uni(a) sort(all(a)), a.resize(unique(all(a))-a.begin())
#define MASK(a) (1ll << a)
int gcd(int x, int y) {return __gcd(x, y) ;}
int lg(int x) {return __lg(x) ;}
int lcm(int x, int y) {return x / __gcd(x, y) * y ;}
template <class T> bool maxi(T &x,T y) { if (x < y) { x = y ; return true ;} return false ;}
template <class T> bool mini(T &x,T y) { if (x > y) { x = y ; return true ;} return false ;}
const int N = 2e3 + 5, M = 5e3 + 5, LG = __lg(N) + 1, base = 311 ;
const int oo = 2e9, sm = 1e9 + 7, mod1 = 1e9 + 7, mod2 = 1e9 + 3 ;
const long long inf = 1e18 ;
int n, p, q ;
ll a[N];
void init() {
cin >> n >> p >> q ;
FOR(i, 1, n) cin >> a[i] ;
sort(a + 1, a + 1 + n) ;
}
int dp[N][N] ;
// dp(i, j) : so lan dung w it de phu 1 ... i va dung j lan 2 * w
bool check(ll w) {
FOR(i, 0, n) FOR(j, 0, min(n, q)) dp[i][j] = oo ;
dp[0][0] = 0 ;
dp[1][0] = 1 ;
dp[1][1] = 0 ;
FOR(i, 2, n) {
int l = 1, r = i, v1 = i ;
while(l <= r) {
int mid = (l + r) >> 1 ;
if(a[mid] >= a[i] - w + 1) v1 = mid, r = mid - 1 ;
else l = mid + 1 ;
}
l = 1, r = i ;
int v2 = i ;
while(l <= r) {
int mid = (l + r) >> 1 ;
if(a[mid] >= a[i] - 1ll * w * 2 + 1) v2 = mid, r = mid - 1 ;
else l = mid + 1 ;
}
FOR(j, 0, min(i, q)) {
if(j > 0) mini(dp[i][j], dp[v2 - 1][j - 1]) ;
mini(dp[i][j], dp[v1 - 1][j] + 1) ;
}
}
int ans = oo ;
FOR(j, 0, min(n, q)) mini(ans, dp[n][j]) ;
return (ans <= p) ;
}
void solve() {
ll l = 1, r = 1e9, ans = - 1 ;
while(l <= r) {
ll mid = (l + r) >> 1 ;
if(check(mid)) ans = mid, r = mid - 1 ;
else l = mid + 1 ;
}
cout << ans ;
}
signed main() {
#define task "paint"
ios_base::sync_with_stdio(0) ; cin.tie(0) ; cout.tie(0) ;
if(fopen(".inp","r")) {
freopen(".inp","r",stdin) ; freopen(".out","w",stdout) ;
}
if(fopen(task".inp","r")) {
freopen(task".inp","r",stdin) ; freopen(task".out","w",stdout) ;
}
init() ;
solve() ;
cerr << "\nTime : " << clock() * 0.001 << "s" << endl ;
return 0 ;
}
/* Watbor */
