#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define mp make_pair
//#define int long long
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define rep(i, l, r) for (int i = (int)(l); i <= (int)(r); i++)
#define per(i, r, l) for (int i = (int)(r); i >= (int)(l); i--)

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

template<typename _Tp> bool minimize(_Tp& __a, const _Tp& __b) { if (__a > __b) { __a = __b; return true; } return false; }
template<typename _Tp> bool maximize(_Tp& __a, const _Tp& __b) { if (__a < __b) { __a = __b; return true; } return false; }

const int siz = 2e3 + 2;
const int SIZ = 1e6 + 2;
const int mod = 1e9 + 7;
const int maxx = 2e9;
const ll MAXX = 1e18;
const string file = "paint";

int n, a, b;
int p[siz];

bool check(int w) {
    int cnt = 0;
    rep (i, 1, n) {
        cnt++;
        int j = i;

        while (j < n && p[j + 1] - p[i] + 1 <= w) {
            /// p[j]  được tô
            j++;
        }
        /// cây cọ p[i] -> p[i] + w - 1

        /// do đó p[j] <= (p[i] + w - 1) sẽ được tô

        /// p[j] - p[i] + 1 <= w

        i = j;
    }

    return cnt <= a;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    if (fopen((file + ".inp").c_str(), "r")) {
        freopen((file + ".inp").c_str(), "r", stdin);
        freopen((file + ".out").c_str(), "w", stdout);
    }

    cin >> n >> a >> b;

    rep (i, 1, n) {
        cin >> p[i];
    }

    if (a + b >= n) {
        cout << 1 << "\n";
        return 0;
    }

    /// các ô đặc biệt sẽ tăng dần

    sort(p + 1, p + n + 1);

    /// p[1] -> p[1] + w - 1

    int ans = -1;
    for (int lb = 1, rb = 1e9; lb <= rb; ) {
        int mb = (lb + rb) / 2;

        if (check(mb)) {
            ans = mb;
            rb = mb - 1;
        } else {
            lb = mb + 1;
        }
    }

    cout << ans << "\n";

//    cerr << "Time: " << 1000 * clock() / CLOCKS_PER_SEC << " ms\n";

    return 0;
}