#include <iostream>

using namespace std;

int main() {
    int N;
    int K;
    cin >> N;
    cin >> K;

    int a[N];
    for ( int i=0; i<N; i++)
        cin >> a[i];
    int l=0;
    int counter;
    int r=a[N-1];
    int d=a[N-1];
    while(1){
        if (r=l) {
            cout << l;
            return 0;
        }


        int q=0;
        counter=0;
        int z=0;
          if (counter > N) {
            l = d-1;
            d=(l + r)/2;
        }
        if (counter <= N) {
            r = d-1;
            d= (l + r) / 2;
            }
        while ( z <= N)  {
            if (a[z]<a[q]+d) {
                    z++;
                    continue;
                }
            if (a[z]>=(a[q]+d)) {
                q=z;
                z++;
                counter++;
                continue;
            }
        }



        }
}