#include<bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(false);cin.tie();cout.tie();
#define all(x) x.begin(), x.end()
#define int long long
#define pq priority_queue
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define pp pop_back
#define F first
#define S second
#define op1 x--; r = a[i] - 1 + k; continue
#define op2 y--; r = a[i] - 1 + 2 * k; continue
using namespace std;
int n, p, q;
int a[2010];
bool check(int k) {
int r = 0;
int x = p, y = q;
for (int i = 1; i <= n; i++) {
if (a[i] <= r) continue ;
if (!x) {if (!y) return 0; op2;}
if (!y) {op1;}
if (a[i+1] - a[i] < 2 * k) {op2;}
else {op1;}
}
return 1;
}
int search(int l, int r) {
while (l < r) {
int m = (l + r) / 2;
if (check(m)) r = m;
else l = m + 1;
}
return l;
}
void solve () {
cin >> n >> p >> q;
for (int i = 1; i <= n; i++) cin >> a[i];
a[n+1] = INT_MAX;
sort(a, a+n+1);
cout << search(1, 1000000000);
}
signed main() {IOS solve(); return 0;}
