#include<cstdio>

#include<algorithm>

#include<cstring>

using namespace std;

const int maxn = 50000 + 10;

int n,k,l,r,mid,ans,d;

int a[maxn];

bool check(int dist) {

    dist=2*dist;

    int d=0,sum=1;

    for(int i=2;i<=n;i++) {

        if(a[i]-a[i-1]>dist-d) {

            sum++;

            d=0;

        }

        else d+=a[i]-a[i-1];

    }

    //printf("%d %d\n",dist/2,sum);

    return sum<=k;

}

int main() {

    scanf("%d%d",&n,&k);

    for(int i=1;i<=n;i++) scanf("%d",&a[i]);

    sort(a+1,a+n+1);

    l=1;r=a[n];

    while(l<r) {

        mid=(l+r)>>1;

        if(check(mid)) r=mid;

        else l=mid+1;

    }

    printf("%d\n",l);

    return 0;

}