//package week3;
import java.io.*;
import java.util.*;
class watching {
public static void main(String[] args) throws IOException {
watching obj = new watching();
obj.doStuff();
}
int bs(int v) {
int l = 0, r = pos.length;
int best = 0;
while (l < r) {
int m = (l+r)/2;
if (v > pos[m]) {
best = m;
l = m+1;
} else r = m;
}
return best;
}
int process(int v) {
dp = new int[pos.length][pos.length+1]; // [pos in array][given x long cams, how many smalls]
for (int i = 1; i < dp.length; i++) {
// just one
int res = bs(pos[i]-v+1);
for (int j = 0; j < dp[0].length; j++) {
dp[i][j] = dp[res][j]+1;
}
// double
res = bs(pos[i]-(2*v)+1);
for (int j = 0; j < dp[0].length-1; j++) {
dp[i][j+1] = Math.min(dp[i][j+1], dp[res][j]);
}
}
return (dp[dp.length-1][Math.min(dp[0].length-1, q)]);
}
int n, p, q;
int[] pos;
int[][] dp;
private void doStuff() throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringTokenizer st = new StringTokenizer(br.readLine());
n = Integer.parseInt(st.nextToken());
p = Integer.parseInt(st.nextToken());
q = Integer.parseInt(st.nextToken());
pos = new int[n+1];
for (int i = 1; i < pos.length; i++) {
pos[i] = Integer.parseInt(br.readLine());
}
br.close();
Arrays.sort(pos);
int l = 1, r = pos[pos.length-1]-pos[1]+1;
int best = 1;
while (l < r) {
int m = (l+r)/2;
int val = process(m);
if (val <= p) {
best = m;
r = m;
} else l = m+1;
}
System.out.println(best);
}
}
