description: You are given an array a[0 … n - 1] = [a_0, a_1, …, a_{n - 1}] of zeroes and ones only. Note that in this problem, unlike the others, the array indexes are numbered from zero, not from one.
  
  In one step, the array a is replaced by another array of length n according to the following rules: 
  
    1. First, a new array a^{→ d} is defined as a cyclic shift of the array a to the right by d cells. The elements of this array can be defined as a^{→ d}_i = a_{(i + n - d) mod n}, where (i + n - d) mod n is the remainder of integer division of i + n - d by n. 
  
  It means that the whole array a^{→ d} can be represented as a sequence $$$a^{→ d} = [a_{n - d}, a_{n - d + 1}, …, a_{n - 1}, a_0, a_1, …, a_{n - d - 1}]$$$
  
    2. Then each element of the array a_i is replaced by a_i  \&  a^{→ d}_i, where \& is a logical "AND" operator. 
  
  
  
  For example, if a = [0, 0, 1, 1] and d = 1, then a^{→ d} = [1, 0, 0, 1] and the value of a after the first step will be [0  \&  1, 0  \&  0, 1  \&  0, 1  \&  1], that is [0, 0, 0, 1].
  
  The process ends when the array stops changing. For a given array a, determine whether it will consist of only zeros at the end of the process. If yes, also find the number of steps the process will take before it finishes.
  
  Input
  
  The first line contains an integer t (1 ≤ t ≤ 1000) — the number of test cases.
  
  The next 2t lines contain descriptions of the test cases. 
  
  The first line of each test case description contains two integers: n (1 ≤ n ≤ 10^6) — array size and d (1 ≤ d ≤ n) — cyclic shift offset. The second line of the description contains n space-separated integers a_i (0 ≤ a_i ≤ 1) — elements of the array.
  
  It is guaranteed that the sum of n over all test cases does not exceed 10^6.
  
  Output
  
  Print t lines, each line containing the answer to the corresponding test case. The answer to a test case should be a single integer — the number of steps after which the array will contain only zeros for the first time. If there are still elements equal to 1 in the array after the end of the process, print -1.
  
  Example
  
  Input
  
  
  5
  2 1
  0 1
  3 2
  0 1 0
  5 2
  1 1 0 1 0
  4 2
  0 1 0 1
  1 1
  0
  
  
  Output
  
  
  1
  1
  3
  -1
  0
  
  Note
  
  In the third sample test case the array will change as follows: 
  
    1. At the beginning a = [1, 1, 0, 1, 0], and a^{→ 2} = [1, 0, 1, 1, 0]. Their element-by-element "AND" is equal to $$$[1  \&  1, 1  \&  0, 0  \&  1, 1  \&  1, 0  \&  0] = [1, 0, 0, 1, 0]$$$ 
    2. Now a = [1, 0, 0, 1, 0], then a^{→ 2} = [1, 0, 1, 0, 0]. Their element-by-element "AND" equals to $$$[1  \&  1, 0  \&  0, 0  \&  1, 1  \&  0, 0  \&  0] = [1, 0, 0, 0, 0]$$$ 
    3. And finally, when a = [1, 0, 0, 0, 0] we get a^{→ 2} = [0, 0, 1, 0, 0]. Their element-by-element "AND" equals to $$$[1  \&  0, 0  \&  0, 0  \&  1, 0  \&  0, 0  \&  0] = [0, 0, 0, 0, 0]$$$ 
  
  Thus, the answer is 3 steps.
  
  In the fourth sample test case, the array will not change as it shifts by 2 to the right, so each element will be calculated as 0  \&  0 or 1  \&  1 thus not changing its value. So the answer is -1, the array will never contain only zeros.
solution: import java.io.BufferedReader;
  import java.io.FileReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.util.StringTokenizer;
  import java.util.Arrays;
  import java.util.Random;
  import java.io.FileWriter;
  import java.io.PrintWriter;
  /*
      Solution Created: 19:31:10 28/09/2021
      Custom Competitive programming helper.
  */
  public class Main {
  	
  	public static void solve() {
  		int n = in.nextInt(), d = in.nextInt();
  		int[] a = in.na(n);
  		 
  		boolean[] vis = new boolean[n];
  		boolean can = true;
  		for(int i = 0; i<n; i++) {
  			if(vis[i]) continue;
  			int and = a[i];
  			for(int j = i; !vis[j]; j = (j+d)%n) {
  				vis[j] = true;
  				and &= a[j];
  			}
  			if(and!=0) can = false;
  		}
  		if(!can) {
  			out.println(-1);
  			return;
  		}
  		int ans = 0;
  		vis = new boolean[n];
  		for(int i = 0; i<n; i++) {
  			if(vis[i]) continue;
  			int moves = 0, val = a[i];
  			int curD = (d+i)%n;
  			while(val!=0) {
  				vis[curD] = true;
  				val &= a[curD];
  				curD = (curD+d)%n;
  				moves++;
  			}
  			ans = Math.max(ans, moves);
  		}
  		out.println(ans);
  	}
  
  	public static void main(String[] args) {
  		in = new Reader();
  		out = new Writer();
  		int t = in.nextInt();
  		while(t-->0) solve();
  		out.exit();
  	}
  	static Reader in; static Writer out;
  
  static class Reader {
  	static BufferedReader br;
  	static StringTokenizer st;
  	
  	public Reader() {
  		this.br = new BufferedReader(new InputStreamReader(System.in));
  	}
  	
  	public Reader(String f){
  		try {
  			this.br = new BufferedReader(new FileReader(f));
  		} catch (IOException e) {
  			e.printStackTrace();
  		}
  	}
  	
  	public int[] na(int n) {
  		int[] a = new int[n];
  		for (int i = 0; i < n; i++) a[i] = nextInt();
  		return a;
  	}
  
  	public double[] nd(int n) {
  		double[] a = new double[n];
  		for (int i = 0; i < n; i++) a[i] = nextDouble();
  		return a;
  	}
  	
  	public long[] nl(int n) {
  		long[] a = new long[n];
  		for (int i = 0; i < n; i++) a[i] = nextLong();
  		return a;
  	}
  
  	public char[] nca() {
  		return next().toCharArray();
  	}
  
  	public String[] ns(int n) {
  		String[] a = new String[n];
  		for (int i = 0; i < n; i++) a[i] = next();
  		return a;
  	}
  
  	public int nextInt() {
  		ensureNext();
  		return Integer.parseInt(st.nextToken());
  	}
  
  	public double nextDouble() {
  		ensureNext();
  		return Double.parseDouble(st.nextToken());
  	}
  
  	public Long nextLong() {
  		ensureNext();
  		return Long.parseLong(st.nextToken());
  	}
  
  	public String next() {
  		ensureNext();
  		return st.nextToken();
  	}
  	
  	public String nextLine() {
  		try {
  			return br.readLine();
  		} catch (Exception e) {
  			e.printStackTrace();
  			return null;
  		}
  	}
  	
  	private void ensureNext() {
  		if (st == null || !st.hasMoreTokens()) {
  			try {
  				st = new StringTokenizer(br.readLine());
  			} catch (IOException e) {
  				e.printStackTrace();
  			}
  		}
  	}
  }
  
  static class Util{
  		private static Random random = new Random();
  		static long[] fact;
  		
  		public static void initFactorial(int n, long mod) {
  			fact = new long[n+1];
  			fact[0] = 1;
  			for (int i = 1; i < n+1; i++) fact[i] = (fact[i - 1] * i) % mod;
  		}
  		
  		public static long modInverse(long a, long MOD) {
  			long[] gcdE = gcdExtended(a, MOD);
  			if (gcdE[0] != 1) return -1; // Inverted doesn't exist
  			long x = gcdE[1];
  			return (x % MOD + MOD) % MOD;
  		}
  		
  		public static long[] gcdExtended(long p, long q) {
  			if (q == 0) return new long[] { p, 1, 0 };
  			long[] vals = gcdExtended(q, p % q);
  			long tmp = vals[2];
  			vals[2] = vals[1] - (p / q) * vals[2];
  			vals[1] = tmp;
  			return vals;
  		}
  		
  		public static long nCr(int n, int r, long MOD) {
  			if (r == 0) return 1;
  			return (fact[n] * modInverse(fact[r], MOD) % MOD * modInverse(fact[n - r], MOD) % MOD) % MOD;
  		}
  		
  		public static long nCr(int n, int r) {
  			return (fact[n]/fact[r])/fact[n-r];
  		}
  		
  		public static long nPr(int n, int r, long MOD) {
  			if (r == 0) return 1;
  			return (fact[n] * modInverse(fact[n - r], MOD) % MOD) % MOD;
  		}
  		public static long nPr(int n, int r) {
  			return fact[n]/fact[n-r];
  		}
  		
  		public static boolean isPrime(int n) { 
  	        if (n <= 1) return false; 
  	        if (n <= 3) return true; 
  	        if (n % 2 == 0 || n % 3 == 0) return false; 
  	        for (int i = 5; i * i <= n; i = i + 6) 
  	            if (n % i == 0 || n % (i + 2) == 0) 
  	            return false; 
  	        return true; 
  	    }
  		
  	    public static boolean[] getSieve(int n) {
  	        boolean[] isPrime = new boolean[n+1];
  	        for (int i = 2; i <= n; i++) isPrime[i] = true;
  	        for (int i = 2; i*i <= n; i++) if (isPrime[i]) 
  	                for (int j = i; i*j <= n; j++) isPrime[i*j] = false;
  	        return isPrime;
  	    }
  	    
  	    static long pow(long x, long pow, long mod){
  	    	long res = 1;
  	    	x = x % mod;
  	    	if (x == 0) return 0;
  	    	while (pow > 0){
  	    		if ((pow & 1) != 0) res = (res * x) % mod;
  	        	pow >>= 1;
  	        	x = (x * x) % mod;
  	    	}
  	    	return res;
  	    }
  	    
  	    public static int gcd(int a, int b) { 
  	    	int tmp = 0;
  	    	while(b != 0) {
  	    		tmp = b;
  	    		b = a%b;
  	    		a = tmp;
  	    	}
  	    	return a;
  	    }
  	    
  	    public static long gcd(long a, long b) { 
  	    	long tmp = 0;
  	    	while(b != 0) {
  	    		tmp = b;
  	    		b = a%b;
  	    		a = tmp;
  	    	}
  	    	return a;
  	    }
  	    
  	    public static int random(int min, int max) {
  	    	return random.nextInt(max-min+1)+min;
  	    }
  	    
  		public static void dbg(Object... o) { 
  			System.out.println(Arrays.deepToString(o)); 
  		}
  		
  		public static void reverse(int[] s, int l , int r) {
  			for(int i = l; i<=(l+r)/2; i++) {
  				int tmp = s[i];
  				s[i] = s[r+l-i];
  				s[r+l-i] = tmp;
  			}
  	    }
  		
  		public static void reverse(int[] s) {
  			reverse(s, 0, s.length-1);
  	    }
  		
  		public static void reverse(long[] s, int l , int r) {
  			for(int i = l; i<=(l+r)/2; i++) {
  				long tmp = s[i];
  				s[i] = s[r+l-i];
  				s[r+l-i] = tmp;
  			}
  	    }
  		
  		public static void reverse(long[] s) {
  			reverse(s, 0, s.length-1);
  	    }
  		
  		public static void reverse(float[] s, int l , int r) {
  			for(int i = l; i<=(l+r)/2; i++) {
  				float tmp = s[i];
  				s[i] = s[r+l-i];
  				s[r+l-i] = tmp;
  			}
  	    }
  		
  		public static void reverse(float[] s) {
  			reverse(s, 0, s.length-1);
  	    }
  		
  		public static void reverse(double[] s, int l , int r) {
  			for(int i = l; i<=(l+r)/2; i++) {
  				double tmp = s[i];
  				s[i] = s[r+l-i];
  				s[r+l-i] = tmp;
  			}
  	    }
  		
  		public static void reverse(double[] s) {
  			reverse(s, 0, s.length-1);
  	    }
  		
  		public static void reverse(char[] s, int l , int r) {
  			for(int i = l; i<=(l+r)/2; i++) {
  				char tmp = s[i];
  				s[i] = s[r+l-i];
  				s[r+l-i] = tmp;
  			}
  	    }
  		
  		public static void reverse(char[] s) {
  			reverse(s, 0, s.length-1);
  	    }
  		
  		public static <T> void reverse(T[] s, int l , int r) {
  			for(int i = l; i<=(l+r)/2; i++) {
  				T tmp = s[i];
  				s[i] = s[r+l-i];
  				s[r+l-i] = tmp;
  			}
  	    }
  		
  		public static <T> void reverse(T[] s) {
  			reverse(s, 0, s.length-1);
  	    }
  		
  		public static void shuffle(int[] s) {
  	        for (int i = 0; i < s.length; ++i) {
  	            int j = random.nextInt(i + 1);
  	            int t = s[i];
  	            s[i] = s[j];
  	            s[j] = t;
  	        }
  	    }
  		
  	    public static void shuffle(long[] s) {
  	        for (int i = 0; i < s.length; ++i) {
  	            int j = random.nextInt(i + 1);
  	            long t = s[i];
  	            s[i] = s[j];
  	            s[j] = t;
  	        }
  	    }
  	    
  	    public static void shuffle(float[] s) {
  	        for (int i = 0; i < s.length; ++i) {
  	            int j = random.nextInt(i + 1);
  	            float t = s[i];
  	            s[i] = s[j];
  	            s[j] = t;
  	        }
  	    }
  	    
  	    public static void shuffle(double[] s) {
  	        for (int i = 0; i < s.length; ++i) {
  	            int j = random.nextInt(i + 1);
  	            double t = s[i];
  	            s[i] = s[j];
  	            s[j] = t;
  	        }
  	    }
  	    
  	    public static void shuffle(char[] s) {
  	        for (int i = 0; i < s.length; ++i) {
  	            int j = random.nextInt(i + 1);
  	            char t = s[i];
  	            s[i] = s[j];
  	            s[j] = t;
  	        }
  	    }
  	    
  	    public static <T> void shuffle(T[] s) {
  	        for (int i = 0; i < s.length; ++i) {
  	            int j = random.nextInt(i + 1);
  	            T t = s[i];
  	            s[i] = s[j];
  	            s[j] = t;
  	        }
  	    }
  	    
  		public static void sortArray(int[] a) {
  	        shuffle(a);
  	        Arrays.sort(a);
  	    }
  		
  		public static void sortArray(long[] a) {
  			shuffle(a);
  	        Arrays.sort(a);
  	    }
  		
  		public static void sortArray(float[] a) {
  			shuffle(a);
  	        Arrays.sort(a);
  	    }
  		
  		public static void sortArray(double[] a) {
  			shuffle(a);
  	        Arrays.sort(a);
  	    }
  		
  		public static void sortArray(char[] a) {
  			shuffle(a);
  	        Arrays.sort(a);
  	    }
  		
  		public static <T extends Comparable<T>> void sortArray(T[] a) {
  	        Arrays.sort(a);
  	    }
  	}
  
  static class Writer {
  	private PrintWriter pw;
  	public Writer(){
  		pw = new PrintWriter(System.out);
  	}
  	
  	public Writer(String f){
  		try {
  			pw = new PrintWriter(new FileWriter(f));
  		} catch (IOException e) {
  			e.printStackTrace();
  		}
  	}
  	
  	public void yesNo(boolean condition) {
  		println(condition?"YES":"NO");
  	}
  	
  	public void printArray(int[] a) {
  		for(int i = 0; i<a.length; i++) print(a[i]+" ");
  	}
  	
  	public void printlnArray(int[] a) {
  		for(int i = 0; i<a.length; i++) print(a[i]+" ");
  		pw.println();
  	}
  	
  	public void printArray(long[] a) {
  		for(int i = 0; i<a.length; i++) print(a[i]+" ");
  	}
  	
  	public void printlnArray(long[] a) {
  		for(int i = 0; i<a.length; i++) print(a[i]+" ");
  		pw.println();
  	}
  	
  	public void print(Object o) {
  		pw.print(o.toString());
  	}
  	
  	public void println(Object o) {
  		pw.println(o.toString());
  	}
  	
  	public void println() {
  		pw.println();
  	}
  	
  	public void flush() {
  		pw.flush();
  	}
  	public void exit() {
  		pw.close();
  	}
  }
  }
  