/* -*- coding: utf-8 -*-
 *
 * 3513.cc:  No.3513 Greedy Yokan Party  - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

/* global variables */

int as[MAX_N + 2];
int dp[MAX_N + 2][3];

/* subroutines */

void setmax(int &a, int b) { if (a < b) a = b; }

int calc(int n, int x) {
  for (int i = 0; i <= n; i++) fill(dp[i], dp[i] + 3, -1);
  dp[0][0] = 0;
  for (int i = 0, i1 = 0; i < n; i++) {
    while (i1 < n && as[i1] - as[i] < x) i1++;
    for (int j = 0; j <= 2; j++)
      if (dp[i][j] >= 0) {
	setmax(dp[i + 1][j], dp[i][j] + 1);
	if (j < 2 && as[i1] - as[i] >= x)
	  setmax(dp[i1][j + 1], dp[i][j] + 1);
      }
  }
  return dp[n][2];
}

/* main */

int main() {
  int n, l, k;
  scanf("%d%d%d", &n, &l, &k);
  as[0] = 0, as[n + 1] = l;
  for (int i = 1; i <= n; i++) scanf("%d", as + i);
  n++;

  int x0 = 0, x1 = l;
  while (x0 + 1 < x1) {
    int x = (x0 + x1) / 2;
    if (calc(n, x) > k) x0 = x;
    else x1 = x;
  }

  printf("%d\n", x0);
  
  return 0;
}