#include<bits/stdc++.h>
#include<fstream>
using namespace std;
ifstream fin("FEEDING.INP");
ofstream fout("FEEDING.OUT");
#define sz(a) (int)a.size()
#define ll long long
#define pb push_back
#define forr(i, a, b) for(int i = a; i < b; i++)
#define dorr(i, a, b) for(int i = a; i >= b; i--)
#define ld long double
#define vt vector
#include<fstream>
#define fi first
#define se second
#define pll pair<ll, ll>
#define pii pair<int, int>
const ld PI = 3.14159265359;
using u128 = __uint128_t;
const int x[4] = {1, -1, 0, 0};
const int y[4] = {0, 0, 1, -1};
const ll mod = 1e9 + 7, inf = 1e9;
const int mxn = 3e5 + 5;
int n, p, q;
int dp[2005][2005], a[2005];
bool ck(int mid){
forr(i, 1, n + 2){
forr(j, 0, p + 1){
dp[i][j] = inf;
}
}
dp[1][0] = 0;
for(int i = 1; i <= n; i++){
for(int j = 0; j <= p; j++){
if(dp[i][j] == inf)continue;
if(j != p){
int idlw = upper_bound(a + 1, a + n + 1, a[i] + mid - 1) - a;
dp[idlw][j + 1] = min(dp[idlw][j + 1], dp[i][j]);
}
int idhg = upper_bound(a + 1, a + n + 1, a[i] + 2 * mid - 1) - a;
dp[idhg][j] = min(dp[idhg][j], dp[i][j] + 1);
}
}
for(int i = 0; i <= p; i++){
if(dp[n + 1][i] <= q)return(1);
}
return(0);
}
signed main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> p >> q; p = min(p, n);
for(int i = 1; i <= n; i++){
cin >> a[i];
}
sort(a + 1, a + n + 1);
int l = 0, r = 5e8, ans = -1;
while(l <= r){
int mid = (l + r) >> 1;
if(ck(mid)){
ans = mid; r = mid - 1;
}else{
l = mid + 1;
}
}
cout << ans;
return(0);
}
