#include<stdio.h>
#include<algorithm>
using namespace std;
int n, k;
int a[51515];
bool f(int x) {
	int i, now = -1e9, cnt = 0;
	for (i = 0; i < n; i++) {
		if (a[i] - now>2 * x)now = a[i], cnt++;
	}
	return cnt <= k;
}
int main() {
	scanf("%d%d", &n, &k);
	for (int i = 0; i < n; i++)scanf("%d", &a[i]);
	sort(a, a + n);
	int s = 0, e = 1e9;
	int ans = 0;
	while (s <= e) {
		int m = (s + e) / 2;
		if (f(m))ans = m, e = m - 1;
		else s = m + 1;
	}
	printf("%d", ans);
	return 0;
}

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