You are given a non-decreasing array of non-negative integers a_1, a_2, …, a_n. Also you are given a positive integer k.

You want to find m non-decreasing arrays of non-negative integers b_1, b_2, …, b_m, such that:

  * The size of b_i is equal to n for all 1 ≤ i ≤ m. 
  * For all 1 ≤ j ≤ n, a_j = b_{1, j} + b_{2, j} + … + b_{m, j}. In the other word, array a is the sum of arrays b_i. 
  * The number of different elements in the array b_i is at most k for all 1 ≤ i ≤ m. 



Find the minimum possible value of m, or report that there is no possible m.

Input

The first line contains one integer t (1 ≤ t ≤ 100): the number of test cases.

The first line of each test case contains two integers n, k (1 ≤ n ≤ 100, 1 ≤ k ≤ n).

The second line contains n integers a_1, a_2, …, a_n (0 ≤ a_1 ≤ a_2 ≤ … ≤ a_n ≤ 100, a_n > 0).

Output

For each test case print a single integer: the minimum possible value of m. If there is no such m, print -1.

Example

Input


6
4 1
0 0 0 1
3 1
3 3 3
11 3
0 1 2 2 3 3 3 4 4 4 4
5 3
1 2 3 4 5
9 4
2 2 3 5 7 11 13 13 17
10 7
0 1 1 2 3 3 4 5 5 6


Output


-1
1
2
2
2
1

Note

In the first test case, there is no possible m, because all elements of all arrays should be equal to 0. But in this case, it is impossible to get a_4 = 1 as the sum of zeros.

In the second test case, we can take b_1 = [3, 3, 3]. 1 is the smallest possible value of m.

In the third test case, we can take b_1 = [0, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2] and b_2 = [0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2]. It's easy to see, that a_i = b_{1, i} + b_{2, i} for all i and the number of different elements in b_1 and in b_2 is equal to 3 (so it is at most 3). It can be proven that 2 is the smallest possible value of m.
//package com.company;


import com.sun.jdi.request.ThreadStartRequest;

import javax.print.attribute.standard.PrinterIsAcceptingJobs;
import javax.sound.midi.spi.SoundbankReader;
import java.awt.*;
import java.awt.image.AreaAveragingScaleFilter;
import java.io.*;
import java.math.BigInteger;
import java.net.Inet4Address;
import java.sql.Array;
import java.sql.SQLOutput;
import java.text.CollationElementIterator;
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.logging.Logger;

public class Main implements Runnable {
    int size[];
    static int e9 = 1000000007;
    int max = Integer.MIN_VALUE;
    long max1 = Long.MIN_VALUE;
    long min1 = Long.MAX_VALUE;
    long fib[][];
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
    int parent[];
    int rank[];
    ArrayList<ArrayList<Integer>> arrayLists;
    long fib1[][];
    long r[];
    int n;
    int m;
    long co=0;
    long size1[];
    long v[];
    int arr[][];
    int u=0;
    HashMap<Long,Long> hashMap=new HashMap<>();
    ArrayList<Long> arrayList;
    public static void main(String[] args) throws IOException {
        new Thread(null,new Main(),"Main",1<<28).start();
    }

    public void run() {
        FastReader scanner = new FastReader();
//            Scanner scanner = new Scanner(System.in);
//            BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter printWriter = new PrintWriter(System.out);
//        System.out.println(10%0);
        long t =scanner.nextLong();
        high:while (t-- > 0) {
           int n=scanner.nextInt();
           int k=scanner.nextInt();
           int arr[]=new int[n];
           Set<Integer> set=new HashSet<>();
           for (int i = 0; i < n; i++) {
               int d = scanner.nextInt();
               arr[i] = d;
           }
           sort(arr,n);
           int s=0;
            for (int i = 1; i < n; i++) {
                if(arr[i]!=arr[i-1]) {
                    s++;
                }
            }
            if(k==1){
                if(s==0){
                    printWriter.println(1);
                }
                else{
                    printWriter.println(-1);
                }
                continue high;
            }
            int u=s/(k-1);
            int v=s%(k-1);
            if(v!=0){
                u++;
            }
            printWriter.println(Math.max(1,u));
        }
        printWriter.flush();
    }
    static long mod=1_000_000_007;
    public long lcm(long a,long b){
        return (a*b)/gcd(a,b);
    }
    public long mul(long a, long b) {
//        System.out.println(a+" "+b);
        return ((a)*(b));
    }
    public long fact(int x) {
        long ans=1;
        for (int i=2; i<=x; i++) ans=mul(ans, i);
        return ans;
    }
    public long fastPow(long base, long exp) {
        if (exp==0) return 1;
        long half=fastPow(base, exp/2);
        if (exp%2==0) return mul(half, half);
        return mul(half, mul(half, base));
    }
    public long modInv(long x) {
        return fastPow(x, mod-2);
    }
    public long nCk(int n, int k) {
        return mul(fact(n), mul(modInv(fact(k)), modInv(fact(n-k))));
    }
    public void parent(int n){
        parent=new int[n+1];
        size=new int[n+1];
        rank=new int[n+1];
        for (int i = 0; i <=n; i++) {
            parent[i]=i;
            rank[i]=0;
//            size[i]=1;
        }
    }
    public void union(int i,int j){
        int root1=find(i);
        int root2=find(j);
//            if(root1 != root2) {
//                parent[root2] = root1;
////                sz[a] += sz[b];
//            }
        if(root1==root2){
            return;
        }
        if(rank[root1]>rank[root2]){
            parent[root2]=root1;
            size[root1]+=size[root2];
        }
        else if(rank[root1]<rank[root2]){
            parent[root1]=root2;
            size[root2]+=size[root1];
        }
        else{
            parent[root2]=root1;
            rank[root1]+=1;
            size[root1]+=size[root2];
        }
    }
    public int find(int p){
        if(parent[p]!=p){
            if(parent[p]==-1){
                return parent[p];
            }
            parent[p]=find(parent[p]);
        }
        return parent[p];
    }
    public double dist(double x1,double y1,double x2,double y2){
        double e=(x2-x1)*(x2-x1)+(y2-y1)*(y2-y1);
        double e1=Math.sqrt(e);
        return e1;
    }
    public void make(int p){
        parent[p]=p;
        rank[p]=1;
    }
    Random rand = new Random();
    public void sort(int[] a, int n) {
        for (int i = 0; i < n; i++) {
            int j = rand.nextInt(i + 1);
            int tmp = a[i];
            a[i] = a[j];
            a[j] = tmp;
        }
        Arrays.sort(a, 0, n);
    }
    public long gcd(long a,long b){
        if(b==0){
            return a;
        }
        return gcd(b,a%b);
    }
    //    public void dfs(ArrayList<Integer> arrayList){
//        for (int i = 0; i < arrayList.size(); i++) {
//            if(v1[arrayList.get(i)]==false){
//                v1[arrayList.get(i)]=true;
//                dfs(arrayLists.get(i));
//            }
//        }
//    }
    public double fact(double h){
        double sum=1;
        while(h>=1){
            sum=(sum%e9)*(h%e9);
            h--;
        }
        return sum%e9;
    }
    public long primef(double r){
        long c=0;
        long ans=1;
        long g=0;
        while(r%2==0){
            c++;
            r=r/2;
        }
        if(c>0){
            ans*=2;
        }
        c=0;
//            System.out.println(ans+" "+r);
        for (int i = 3; i <=Math.sqrt(r) ;i+=2) {
            g=0;
            while(r%i==0){
//                    System.out.println(i);
                c++;
                g++;
                r=r/i;
            }
            if(c>0){
                ans*=i;
            }
            c=0;
        }
        if(r>2){
            ans*=r;
        }
        return ans;
    }
    public long divisor(double r){
        long c=0;
//        if(n==3)
//            System.out.println(r+" "+n+" "+k+" "+"l");
        for (int i =2; i <=Math.sqrt(r); i++) {
            if(r%i==0){
                if(r/i==i){
                    c++;
                }
                else{
                    if(r/i<n){
                        c+=2;
                    }else{
                        c++;
                    }
                }
            }
        }
        return c;
    }
}
class Pair {
    int x;
    int y;
    int z;
    public Pair(int x,int y) {
        this.x = x;
        this.y = y;
//        this.z=z;
    }

     @Override
    public int hashCode() {
        int hash = 37;
        return this.x * hash + this.y;
    }

    @Override
    public boolean equals(Object o1) {
        if (o1 == null || o1.getClass() != this.getClass()) {
            return false;
        }
        Pair o = (Pair) o1;
        if (o.x == this.x && o.y == this.y) {
            return true;
        }
        return false;
    }
}
class Sorting implements Comparator<Pair> {
    public int compare(Pair p1, Pair p2) {
        if(p1.x==p2.x){
            return Long.compare(p1.y,p2.y);
        }else {
            return Long.compare(p1.x, p2.x);
        }
    }
}
class Edge{
    int s=0;
    int d=0;
    int c=0;
    public Edge(int s,int d,int c){
        this.s=s;
        this.d=d;
        this.c=c;
    }
}