This morning, Roman woke up and opened the browser with n opened tabs numbered from 1 to n. There are two kinds of tabs: those with the information required for the test and those with social network sites. Roman decided that there are too many tabs open so he wants to close some of them.

He decided to accomplish this by closing every k-th (2 ≤ k ≤ n - 1) tab. Only then he will decide whether he wants to study for the test or to chat on the social networks. Formally, Roman will choose one tab (let its number be b) and then close all tabs with numbers c = b + i ⋅ k that satisfy the following condition: 1 ≤ c ≤ n and i is an integer (it may be positive, negative or zero).

For example, if k = 3, n = 14 and Roman chooses b = 8, then he will close tabs with numbers 2, 5, 8, 11 and 14.

After closing the tabs Roman will calculate the amount of remaining tabs with the information for the test (let's denote it e) and the amount of remaining social network tabs (s). Help Roman to calculate the maximal absolute value of the difference of those values |e - s| so that it would be easy to decide what to do next.

Input

The first line contains two integers n and k (2 ≤ k < n ≤ 100) — the amount of tabs opened currently and the distance between the tabs closed.

The second line consists of n integers, each of them equal either to 1 or to -1. The i-th integer denotes the type of the i-th tab: if it is equal to 1, this tab contains information for the test, and if it is equal to -1, it's a social network tab.

Output

Output a single integer — the maximum absolute difference between the amounts of remaining tabs of different types |e - s|.

Examples

Input


4 2
1 1 -1 1


Output


2


Input


14 3
-1 1 -1 -1 1 -1 -1 1 -1 -1 1 -1 -1 1


Output


9

Note

In the first example we can choose b = 1 or b = 3. We will delete then one tab of each type and the remaining tabs are then all contain test information. Thus, e = 2 and s = 0 and |e - s| = 2.

In the second example, on the contrary, we can leave opened only tabs that have social networks opened in them.
import java.io.BufferedWriter;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.io.OutputStreamWriter;
	import java.io.PrintWriter;
	import java.io.Writer;
	import java.util.Arrays;
	import java.util.InputMismatchException;
	import java.util.*;
	import java.io.*;
	import java.math.*;
public class Main{

	static class Pair
		{ 
			int x; 
			int y; 
			//int z;
			public Pair(int x, int y) 
			{	 
				this.x = x; 
				this.y = y; 
				
			}	 
		} 
		static class Compare
		{ 
			static void compare(Pair arr[], int n) 
			{ 
				// Comparator to sort the pair according to second element 
				Arrays.sort(arr, new Comparator<Pair>() { 
					@Override public int compare(Pair p1, Pair p2) 
					{ 
						return p1.y - p2.y; 
					} 
				}); 
			} 
		}
		public static long pow(long a, long b)
		{
			long result=1;
			while(b>0)
			{
				if (b % 2 != 0)
				{
					result=(result*a)%(mod);
					b--;
				} 
				a=(a*a)%(mod);
				b /= 2;
			}   
			return result;
		}
		public static long fact(long num)
		{
					long value=1;
					int i=0;
					for(i=2;i<num;i++)
					{
						value=((value%mod)*i%mod)%mod;
					}
					return value;
				}
				public static long gcd(long a, long b)
				{
					if (a == 0)
						return b;
					return gcd(b%a, a);
				}
				
				public static long lcm(int a,int b)
				{
					return a * (b / gcd(a, b));
				}
				public static long sum(int h)
				{
					return (h*(h+1)/2);
				}
				public static void dfs(int parent,boolean[] visited,int k)
				{
					ArrayList<Integer> arr=new ArrayList<Integer>();
					arr=graph.get(parent);
					visited[parent]=true;
					if(parent!=0)
					{
						fin[k]=parent;
						k+=2;
					}if(arr.size()==0)
						return;
					for(int i=0;i<arr.size();i++)
					{
						int num=arr.get(i);
						if(visited[num]==false)
						{
							dfs(num,visited,k);
						}
					}
				}
				public static void dfs1(int parent,boolean[] visited,int k)
				{
					ArrayList<Integer> arr=new ArrayList<Integer>();
					arr=graph.get(parent);
					visited[parent]=true;
					if(parent!=0)
					{
						fin[k]=parent;
						k-=2;
					}
					if(arr.size()==0)
						return;
					for(int i=0;i<arr.size();i++)
					{
						int num=arr.get(i);
						if(visited[num]==false)
						{
							dfs(num,visited,k);
						}
					}
				}
				static int[] fin;
			//	static int[] count;
				static int f=0;
				static char[] ch;
				static long mod=998244353L;
				static int[] b;
				static int[] a;
				static ArrayList<ArrayList<Integer>> graph;
				public static void main(String args[])throws IOException
				{
					InputReader in=new InputReader(System.in);
					OutputWriter out=new OutputWriter(System.out);
				//	long a=pow(26,1000000005);
				//    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
					ArrayList<Integer> ar=new ArrayList<>();
					ArrayList<Integer> ar1=new ArrayList<>();
					ArrayList<Integer> ar2=new ArrayList<>();
					ArrayList<Integer> ar3=new ArrayList<>();
					ArrayList<Integer> ar4=new ArrayList<>();
					TreeSet<Integer> ts=new TreeSet<>();
					TreeSet<Integer> ts1=new TreeSet<>();
					TreeSet<String> pre=new TreeSet<>();
					HashMap<Integer,Integer> hash=new HashMap<>();
					HashMap<Long,Integer> hash1=new HashMap<Long,Integer>();
					HashMap<Long,Integer> hash2=new HashMap<Long,Integer>();
					Map<Integer, List<Integer>> hml = new HashMap<>(); 
				/*	boolean[] prime=new boolean[100001];
					for(int i=2;i*i<=100000;i++)
					{
						if(prime[i]==false)
						{
							for(int j=2*i;j<=100000;j+=i)
							{
								prime[j]=true;
							}
						}
					}*/
					int n=i();
					int k=i();
					int a[]=new int[n];
					int suma=0,sumb=0;
					for(int i=0;i<n;i++)
					{
						a[i]=i();
						if(a[i]>0)
							suma+=a[i];
						else
						sumb+=1;
					}
					int sum1a,sum1b;int max=0;
					for(int i=0;i<k;i++)
					{
						sum1a=suma;sum1b=sumb;
						for(int j=i;j<n;j+=k)
						{
							if(a[j]==1)
							{
								sum1a=sum1a-1;
							}
							else
								sum1b=sum1b-1;
						}
						if(Math.abs(sum1a-sum1b)>max)
						{
							max=Math.abs(sum1a-sum1b);
							//System.out.println(max);
							//pln(""+sum1a);
							//pln(""+sum1b);
						}
					}
					
					pln(""+max);
				}					
					
				     
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				/**/
				static InputReader in=new InputReader(System.in);
					static OutputWriter out=new OutputWriter(System.out);
					public static long l()
					{
						String s=in.String();
						return Long.parseLong(s);
					}
					public static void pln(String value)
					{
						System.out.println(value);
					}
					public static int i()
					{
						return in.Int();
					}
					public static String s()
					{
						return in.String();
					}
		}
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			class InputReader {
				 
				private InputStream stream;
				private byte[] buf = new byte[1024];
				private int curChar;
				private int numChars;
				private SpaceCharFilter filter;
			 
				public InputReader(InputStream stream) {
					this.stream = stream;
				}
			 
				public int read() {
					if (numChars== -1)
						throw new InputMismatchException();
					if (curChar >= numChars) {
						curChar = 0;
						try {
							numChars = stream.read(buf);
						} catch (IOException e) {
							throw new InputMismatchException();
						}
						if (numChars <= 0)
							return -1;
					}
					return buf[curChar++];
				}
			 
				public int Int() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					int sgn = 1;
					if (c == '-') {
						sgn = -1;
						c = read();
					}
					int res = 0;
					do {
						if (c < '0' || c > '9')
							throw new InputMismatchException();
						res *= 10;
						res += c - '0';
						c = read();
					} while (!isSpaceChar(c));
					return res * sgn;
				}
			 
				public String String() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					StringBuilder res = new StringBuilder();
					do {
						res.appendCodePoint(c);
						c = read();
					} while (!isSpaceChar(c));
					return res.toString();
				}
			 
				public boolean isSpaceChar(int c) {
					if (filter != null)
						return filter.isSpaceChar(c);
					return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
				}
			 
				public String next() {
					return String();
				}
			 
				public interface SpaceCharFilter {
					public boolean isSpaceChar(int ch);
				}
			}
			 
			class OutputWriter {
				private final PrintWriter writer;
			 
				public OutputWriter(OutputStream outputStream) {
					writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
				}
			 
				public OutputWriter(Writer writer) {
					this.writer = new PrintWriter(writer);
				}
			 
				public void print(Object...objects) {
					for (int i = 0; i < objects.length; i++) {
						if (i != 0)
							writer.print(' ');
						writer.print(objects[i]);
					}
				}
			 
				public void printLine(Object...objects) {
					print(objects);
					writer.println();
				}
			 
				public void close() {
					writer.close();
				}
			 
				public void flush() {
					writer.flush();
				}
			 
				}
			 
				class IOUtils {
			 
				public static int[] readIntArray(InputReader in, int size) {
					int[] array = new int[size];
					for (int i = 0; i < size; i++)
						array[i] = in.Int();
					return array;
				}
			 
				} 