#include <bits/stdc++.h>
using namespace std;
int a, b, c, d, n[10000], low, maxx, mid, ls, aaa, la[10000];
bool ch(int mid) {
    int bus, st = n[1], cow;
    for (int i = 2; i <= a; i++) {
        cow++;
        if (n[i] - st > mid || cow > c) {
            bus++;
            cow = 1;
            st = n[i];
            if (bus > b)
                return 0;
        }
    }
    return 1;
}
int main() {
    cin >> a >> b >> c;
    for (int i = 1; i <= a; i++) {
        cin >> n[i];
    }
    sort(n, n + a + 1);
    int l = 0, r = 100000000;
    while (l < r) {
        mid = (l + r + 1) / 2;
        if (ch(mid))
            l = mid;
        else
            r = mid - 1;
    }
    cout << l;
}