#include <iostream>
#include <vector>
#include <algorithm>
#include <climits>
using namespace std;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int N, P, Q;
cin >> N >> P >> Q;
vector<int> A(N);
for (int i = 0; i < N; i++) {
cin >> A[i];
}
sort(A.begin(), A.end());
A.erase(unique(A.begin(), A.end()), A.end());
int n = A.size();
if (n == 0) {
cout << 0 << endl;
return 0;
}
int low = 1;
int high = 1000000000;
int ans = high;
while (low <= high) {
int w = low + (high - low) / 2;
vector<int> small_cover(n), large_cover(n);
for (int i = 0; i < n; i++) {
long long end_small = (long long)A[i] + w - 1;
auto it_small = upper_bound(A.begin(), A.end(), end_small);
small_cover[i] = it_small - A.begin() - 1;
long long end_large = (long long)A[i] + 2 * w - 1;
auto it_large = upper_bound(A.begin(), A.end(), end_large);
large_cover[i] = it_large - A.begin() - 1;
}
int max_j = min(n, Q);
vector<vector<int>> dp(n + 1, vector<int>(max_j + 1, INT_MAX / 2));
dp[0][0] = 0;
for (int i = 0; i < n; i++) {
for (int j = 0; j <= max_j; j++) {
if (dp[i][j] == INT_MAX / 2) continue;
int next_small = small_cover[i] + 1;
if (next_small <= n) {
dp[next_small][j] = min(dp[next_small][j], dp[i][j] + 1);
}
if (j < max_j) {
int next_large = large_cover[i] + 1;
if (next_large <= n) {
dp[next_large][j + 1] = min(dp[next_large][j + 1], dp[i][j]);
}
}
}
}
bool possible = false;
for (int j = 0; j <= max_j; j++) {
if (dp[n][j] <= P) {
possible = true;
break;
}
}
if (possible) {
ans = w;
high = w - 1;
} else {
low = w + 1;
}
}
cout << ans << endl;
return 0;
}
