#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, U b) {
  if (a < b) a = b;
}
template <typename T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T, class T1>
inline void gn(T &first, T1 &second) {
  gn(first);
  gn(second);
}
template <class T, class T1, class T2>
inline void gn(T &first, T1 &second, T2 &z) {
  gn(first);
  gn(second);
  gn(z);
}
template <typename T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <typename T>
inline void println(T first) {
  print(first), putchar('\n');
}
template <typename T>
inline void printsp(T first) {
  print(first), putchar(' ');
}
template <class T, class T1>
inline void print(T first, T1 second) {
  printsp(first), println(second);
}
template <class T, class T1, class T2>
inline void print(T first, T1 second, T2 z) {
  printsp(first), printsp(second), println(z);
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
int a[5050];
int E, head[1000100], nxt[5050 * 5050 / 2];
pair<int, int> to[5050 * 5050 / 2];
int flag[5050], runs;
int idflag[1000100];
int add(int u, int v, int m) {
  int id = a[u] % m;
  if (idflag[id] != runs) {
    idflag[id] = flag[u] = flag[v] = runs;
    return 1;
  }
  int ans = 0;
  if (flag[u] != runs) flag[u] = runs, ans++;
  if (flag[v] != runs) flag[v] = runs, ans++;
  return ans;
}
int main() {
  int n, k;
  gn(n, k);
  for (int i = 0; i < n; i++) gn(a[i]);
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      int d = abs(a[i] - a[j]);
      E++;
      nxt[E] = head[d];
      to[E] = pair<int, int>(i, j);
      head[d] = E;
    }
  }
  for (int i = 1; i < 1000100; i++) {
    runs++;
    int ct = 0;
    for (int j = i; j < 1000100 && ct <= k; j += i) {
      for (int e = head[j]; e && ct <= k; e = nxt[e]) {
        ct += add(to[e].first, to[e].second, i);
      }
    }
    if (ct <= k) {
      println(i);
      return 0;
    }
  }
  return 0;
}
