#include <iostream>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <vector>
#include <tuple>
#define endl "\n"
#define int long long int
#define ld long double
#define mp make_pair
#define pb push_back
#define Bound 2e5+1
using namespace std;
bool comp(pair<int, int> a, pair<int, int> b) {
return a.second < b.second;
}
int32_t main()
{
int n, p, q;
cin >> n >> p >> q;
if (p + q >= n) {
cout << 0;
return 0;
}
int* a = new int[n];
for (int i = 0; i < n; i++) {
cin >> a[i];
}
sort(a, a + n);
vector<pair<int,int>> b(n-1);
for (int i = 0; i < n - 1; i++) {
b[i] = mp(a[i + 1] - a[i] + 1,i);
}
sort(b.rbegin(), b.rend());
for (int i = 0; i < p + q - 1; i++) {
b[i].first = -1;
}
sort(b.begin(), b.end(), comp);
vector<int> measure;
int size = 0;
for (int i = 0; i < n - 1; i++) {
if (b[i].first != -1) size += b[i].first;
else {
measure.pb(size);
size = 0;
}
}
if(size != 0) {
measure.pb(size);
}
sort(measure.rbegin(), measure.rend());
int w = 0;
for (int i = 0; i < measure.size(); i++) {
if (q > 0) {
w = max(w, (measure[i] + 1) / 2);
q--;
}
else w = max(w, measure[i]);
}
cout << w;
return 0;
}
