#include<iostream>
#include<algorithm>
using namespace std;
int n;
int c;
int ans;
int a[200010];
bool Chk(int g){
	int cow = 1;
	int loc = a[1];
	for(int i = 2;i <= n;i ++){
		if(a[i] - loc >= g){
			cow ++;
			loc = a[i];
			if(cow >= c){
				return true;
			}
		}
	}
	return false;
}
int main(){
	cin >> n >> c;
	for(int i = 1;i <= n;i ++){
		cin>>a[i];
	}
	int l = 1;
	int r = n;
	int m = 0;
	while(l <= r){
		m = (l + r) / 2;
		if(Chk(m)){
			ans = m;
			l = m + 1;
		}
		else{
			r = m - 1;
		}
	}
	cout << ans;
	return 0;
}