#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int n;
vector <ll> jalur;
bool cek(int p, int q, int k, ll last) {
if (last>=n) return true;
if (p==0&&q==0) return false;
bool a=false, b=false;
if (q>0) {
ll jq=jalur[last]-1+(k*2);
ll akhir = upper_bound(jalur.begin(), jalur.end(), jq) - jalur.begin();
a = cek(p, q-1, k, akhir);
}
if (a) return true;
if (p>0) {
ll jp=jalur[last]-1+k;
ll akhir = upper_bound(jalur.begin(), jalur.end(), jp) - jalur.begin();
b = cek(p-1, q, k, akhir);
}
return a||b;
}
int main() {
int p, q; cin >> n >> p >> q;
for (int i=0;i<n;i++) {
ll x; cin >> x;
jalur.push_back(x);
}
sort(jalur.begin(), jalur.end());
ll kiri=1, kanan = 1e9, mid, ans=1;
while (kiri<=kanan) {
mid = (kiri+kanan)/2;
if (cek(p, q, mid, 0)) {
ans = mid;
kanan = mid-1;
} else {
kiri = mid+1;
}
}
cout << ans << endl;
return 0;
}
