#include<stdio.h>
int a[200005];
int left[200005], right[200005];
int main()
{
	int n, l, k;
	scanf("%d %d %d", &n, &l, &k);
	int i, j;
	for (i = 0; i < n; i++)
		scanf("%d", &a[i + 1]);
	a[0] = 0;
	a[++n] = l;
	int min, mid, max;
	min = 0;
	max = l + 1;
	while (max - min > 1)
	{
		mid = (max + min) / 2;
		left[0] = 1e9;
		for (j = 0, i = 1; i <= n; i++)
		{
			for (; a[i] - a[j + 1] >= mid; j++);
			if (a[i] - a[j] < mid)
				left[i] = 1e9;
			else if (left[i - 1] > i - j - 1)
				left[i] = i - j - 1;
			else
				left[i] = left[i - 1];
		}
		right[n] = 1e9;
		for (i = n - 1, j = n; i >= 0; i--)
		{
			for (; a[j - 1] - a[i] >= mid; j--);
			if (a[j] - a[i] < mid)
				right[i] = 1e9;
			else if (right[i + 1] > j - i - 1)
				right[i] = j - i - 1;
			else
				right[i] = right[i + 1];
		}
		j = 1e9;
		for (i = 0; i <= n; i++)
			if (j > left[i] + right[i])
				j = left[i] + right[i];
		if (j + k > n - 1)
			max = mid;
		else
			min = mid;
	}
	printf("%d\n", min);
	return 0;
}