#include <iomanip>
#include <cmath>
using namespace std;

int a[10000]; int k;	int ii = 0;
int f(int m){
	int kol=0;
	for (int i = 0; i < k; i++){
		if (a[i + 1] - a[i]>m)
		{
			kol++;
		}
	}
	return kol;
}
int main()
{

	int n;

	cin >>k>> n;
	for (int i = 0; i < k; i++){
		cin >> a[i];
	}

	int  L = a[0];
	int R = a[k-1];
	int M = (L + R) / n-1;
	while(R - L > 1)
	{


		if (f(M)>n) {
			L = f(M);
		} else {
			R = f(M);
		}
	}
	cout << R;
}