#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(), x.rend()
#define int long long
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int MAXN = 1e5+10;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3f;
const int MOD = 1e9+7;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
int n, p, q;
vector<int> arr;
bool check(int w){
vector<vector<int>> dp(n+1, vector<int>(p+1, INF));
dp[0][0]=0;
int ptr1=0, ptr2=0;
for(int i=1;i<=n;i++){
while(arr[ptr1+1]<=arr[i]-w) ptr1++;
while(arr[ptr2+1]<=arr[i]-2*w) ptr2++;
for(int j=0;j<=p;j++){
if(j) dp[i][j]=min(dp[i][j], dp[ptr1][j-1]);
dp[i][j]=min(dp[i][j], dp[ptr2][j]+1);
}
}
int mn=INF;
for(int i=0;i<=p;i++) mn=min(mn, dp[n][i]);
return mn<=q;
}
void solve(){
cin >> n >> p >> q; p=min(p, n);
arr.resize(n+1); arr[0]=-INF;
for(int i=1;i<=n;i++) cin >> arr[i];
sort(arr.begin()+1, arr.end());
int l=1, r=5e8, best=-1;
while(l<=r){
int mid=(l+r)>>1;
if(check(mid)){
best=mid;
r=mid-1;
}
else l=mid+1;
}
cout << best << "\n";
}
int32_t main(){
ios_base::sync_with_stdio(false); cin.tie(NULL);
int tt=1;
//cin >> tt;
while(tt--) solve();
return 0;
}
