Untitled

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
ll pos[100005];
ll N, M;

bool Condition(ll x){
  ll car_pos = 1;
  ll last_pos = pos[0];
  for(ll i = 1; i < N; i++){
    if(pos[i] - last_pos >= x){
      last_pos = pos[i];
      car_pos++;
      if(car_pos == M){
        return 1;
      }
    }
  }
  return 0;
}

ll binarySearch(){
  ll start = 0;
  ll end = pos[N - 1];
  ll ans = -1;
  while(start < end){
    int mid = start + (end - start)/2;
    if(Condition(mid) == 1){
      if(mid > ans){
        ans = mid;
      }
      start = mid + 1;
    }
    else{
      end = mid;
    }
  }
  return ans;
}

int main() {

    cin >> N >> M;
    for(int i = 0;i<N;i++){
        cin >> pos[i];
    }
    sort(pos, pos + N);
    cout << binarySearch();
  return 0;
}