Innokentiy likes tea very much and today he wants to drink exactly n cups of tea. He would be happy to drink more but he had exactly n tea bags, a of them are green and b are black.

Innokentiy doesn't like to drink the same tea (green or black) more than k times in a row. Your task is to determine the order of brewing tea bags so that Innokentiy will be able to drink n cups of tea, without drinking the same tea more than k times in a row, or to inform that it is impossible. Each tea bag has to be used exactly once.

Input

The first line contains four integers n, k, a and b (1 ≤ k ≤ n ≤ 105, 0 ≤ a, b ≤ n) — the number of cups of tea Innokentiy wants to drink, the maximum number of cups of same tea he can drink in a row, the number of tea bags of green and black tea. It is guaranteed that a + b = n.

Output

If it is impossible to drink n cups of tea, print "NO" (without quotes).

Otherwise, print the string of the length n, which consists of characters 'G' and 'B'. If some character equals 'G', then the corresponding cup of tea should be green. If some character equals 'B', then the corresponding cup of tea should be black.

If there are multiple answers, print any of them.

Examples

Input

5 1 3 2


Output

GBGBG


Input

7 2 2 5


Output

BBGBGBB

Input

4 3 4 0


Output

NO
import java.util.*;
import java.io.*;
public class GreenandBlackTea
{


	/************************ SOLUTION STARTS HERE ***********************/

	static String rec (int idx , int N , int K , int a , int b , int streak , char ch , String curr) {

		if(streak > K)
			return null;
		if(idx == N)
			return curr;
		else {
			if(a > 0) {
				String s = rec(idx + 1, N, K, a - 1, b, ch == 'G' ? streak + 1 : 1, 'G', curr + 'G');
				if(s != null)
					return s;
			}
			if(b > 0) {
				String s = rec(idx + 1, N, K, a, b - 1, ch == 'B' ? streak + 1 : 1, 'B', curr + 'B');
				if(s != null)
					return s;
			}
			return null;
		}
		
	}

	private static void solve(FastScanner s1, PrintWriter out){

		int N = s1.nextInt();
		int K = s1.nextInt();
		int a = s1.nextInt();
		int b = s1.nextInt();

		String s = rec(0, N, K, a, b, 1, '*', "*");
		
		if(s == null)
			out.println("NO");
		else
			out.println(s.substring(1));
	}
	
	private static void solve2(FastScanner s1, PrintWriter out){

		int N = s1.nextInt();
		int K = s1.nextInt();
		int a = s1.nextInt();
		int b = s1.nextInt();
		
		char sm , bi;
		int min , max;
		if(a <= b) {
			min = a;
			max = b;
			sm = 'G';
			bi = 'B';
		}
		else {
			min = b;
			max = a;
			sm = 'B';
			bi = 'G';
		}
		
		StringBuilder sb1 = new StringBuilder();
		int streak = 1;
		sb1.append(bi);
		for(int i=1;i<max;i++) {
			if(streak == K) {
				if(min > 0) {
					min--;
					sb1.append(sm);
					streak = 0;
				}
				else {
					out.println("NO");
					return;
				}
			}
			sb1.append(bi);
			streak++;
		}
		
		if(min == 0) {
			out.println(sb1);
			return;
		}
		
		StringBuilder sb2 = new StringBuilder();
		int ptr = 0;
		
		// out.println("sb1 " + sb1);
		
		while(ptr < sb1.length() && min > 0) {
			if(sb1.charAt(ptr) == bi) {
				for(int i=1;i<=Math.min(K,min);i++)
					sb2.append(sm);
				sb2.append(bi);
				ptr++;
				min -= Math.min(min,K);
			}
			else {
				for(int i=1;i<=Math.min(K,min);i++)
					sb2.append(sm);
				ptr++;
				if(ptr < sb1.length()) {
					sb2.append(bi);
					ptr += 2;
				}
				min -= Math.min(min,K);
			}
		}
		
		if(ptr < sb1.length())
			sb2.append(sb1.substring(ptr));
		
		// out.println(sb2);
		
		if(min > 0)
			out.println("NO");
		else
			out.println(sb2);
		
	}

	private static void solve3(FastScanner s1, PrintWriter out){

		int N = s1.nextInt();
		int K = s1.nextInt();
		int a = s1.nextInt();
		int b = s1.nextInt();
		char sm , bi;
		int min , max;
		if(a <= b) {
			min = a;
			max = b;
			sm = 'G';
			bi = 'B';
		}
		else {
			min = b;
			max = a;
			sm = 'B';
			bi = 'G';
		}
		
		if(max * 1L > 1L * (min + 1) * K)
			out.println("NO");
		else {
			int bins = min + 1;
			StringBuilder ans = new StringBuilder();
			StringBuilder rep = new StringBuilder();
			for(int i=1;i<=(max / bins);i++)
				rep.append(bi);
			
			for(int i=1;i<=(max % bins);i++)
				ans.append(rep).append(bi).append(sm);
			for(int i=max % bins;i < bins - 1;i++)
				ans.append(rep).append(sm);
			ans.append(rep);
			
			out.println(ans);
		}
		
	}
		/************************ SOLUTION ENDS HERE ************************/





		/************************ TEMPLATE STARTS HERE *********************/

		public static void main(String []args) throws IOException {
			FastScanner in  = new FastScanner(System.in);
			PrintWriter out = 
					new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)), false); 
			solve3(in, out);
			in.close();
			out.close();
		}    

		static class FastScanner{
			BufferedReader reader;
			StringTokenizer st;
			FastScanner(InputStream stream){reader=new BufferedReader(new InputStreamReader(stream));st=null;}	
			String next()
			{while(st == null || !st.hasMoreTokens()){try{String line = reader.readLine();if(line == null){return null;}		    
			st = new StringTokenizer(line);}catch (Exception e){throw new RuntimeException();}}return st.nextToken();}
			String nextLine()  {String s=null;try{s=reader.readLine();}catch(IOException e){e.printStackTrace();}return s;}	    	  	
			int    nextInt()   {return Integer.parseInt(next());}
			long   nextLong()  {return Long.parseLong(next());}		
			double nextDouble(){return Double.parseDouble(next());}
			char   nextChar()  {return next().charAt(0);}
			int[]  nextIntArray(int n)         {int[] a= new int[n];   int i=0;while(i<n){a[i++]=nextInt();}  return a;}
			long[] nextLongArray(int n)        {long[]a= new long[n];  int i=0;while(i<n){a[i++]=nextLong();} return a;}	
			int[]  nextIntArrayOneBased(int n) {int[] a= new int[n+1]; int i=1;while(i<=n){a[i++]=nextInt();} return a;}	    	
			long[] nextLongArrayOneBased(int n){long[]a= new long[n+1];int i=1;while(i<=n){a[i++]=nextLong();}return a;}	    	
			void   close(){try{reader.close();}catch(IOException e){e.printStackTrace();}}				
		}

		/************************ TEMPLATE ENDS HERE ************************/
	}