import java.util.Arrays;
import java.util.List;

public class Solution {

    public static boolean c(int mid, List<Integer> a) {
        int ct = 1;
        int st = a.get(0);
        for (int i = 1; i < a.size(); i++) {
            if (st + mid < a.get(i)) {
                st = a.get(i);
                ct++;
            }
            if (ct > 2)
                return false;
        }
        return true;
    }

    public static int solution(List<Integer> a) {
        a.sort(null);
        int l = 1, r = Integer.MAX_VALUE;
        int ans = r;
        while (l <= r) {
            int mid = (l + r) / 2;
            if (c(mid, a)) {
                ans = mid;
                r = mid - 1;
            } else
                l = mid + 1;
        }
        return ans;
    }

    public static void main(String[] args) {
        List<Integer> a = Arrays.asList(3, 6, 9, 12, 15);
        System.out.println(solution(a));
    }
}