#include <bits/stdc++.h>

using namespace std;

using pii = pair<int, int>;
using ll = long long;
const int N = 2000010, MOD = 998244353, INF = 0x3f3f3f3f;
int n, m, w[N];

int k;
bool check(int mid) {
    vector<int> l(n + 1, INF), r(n + 1, INF);
    for (int i = 1; i < n + 1; i++) {
        if (w[i] >= mid) {
            auto u = upper_bound(w, w + n + 1, w[i] - mid);
            --u;
            l[i] = w + i - u;
        }
        l[i] = min(l[i], l[i - 1]);
    }
    for (int i = n; i; i--) {
        if (w[n] - w[i - 1] >= mid) {
            auto u = lower_bound(w, w + n + 1, w[i - 1] + mid);
            r[i] = u - (w + i) + 1;
        }
    }
    for (int i = n; i > 1; i--)
        if (r[i] + l[i - 1] <= n - (k - 1))
            return 1;
    return 0;
}

void solve() {
    scanf("%d%d%d", &n, &m, &k);
    for (int i = 1; i < n + 1; i++) scanf("%d", w + i);
    ++n, w[n] = m;

    int l = 1, r = 1e9;
    while (l < r) {
        int mid = l + r + 1 >> 1;
        if (check(mid)) l = mid;
        else r = mid - 1;
    }
    printf("%d\n", l);
}

int main() {
    int T = 1;
    // scanf("%d", &T);
    while (T--) solve();
    return 0;
}