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.io.BufferedReader;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.math.BigInteger;


import java.util.*;

public class random_num {
public static long x,y,d;
public static int mod= (int) (Math.pow(10,9)+7);
	public static void main(String args[]){
		InputReader s= new InputReader(System.in);
		OutputStream outputStream= System.out;
		PrintWriter out= new PrintWriter(outputStream);
		int n= s.nextInt();
		int k= s.nextInt();
		int a= s.nextInt();
		int b= s.nextInt();
		int max = k;
	
		char ans[]= new char[n];
		
		for(int i=0;i<n;i++){
			if(k==0 && i!=0){
				if(ans[i-1]=='B'){
					ans[i]='G';
					a--;
					k=max;
				}
				else{
					ans[i]='B';
					b--;
					k=max;
				}
				continue;
			}
			int x = Math.max(a, b);
			if(x==a){
				ans[i]= 'G';
					k--;
					a--;
			}
			else{
				ans[i]= 'B';
				k--;
				b--;
			}
		}
		if(a<0 || b<0)
			out.println("NO");
		else{
			for(int i=0;i<n;i++){
				out.print(ans[i]);
			}
		}
		out.close();
	}
	static class InputReader {
		
	    public BufferedReader reader;
	    public StringTokenizer tokenizer;
 
	    public InputReader(InputStream inputstream) {
	      reader = new BufferedReader(new InputStreamReader(inputstream));
	      tokenizer = null;
	    }
	    
	    public String nextLine(){
	    	String fullLine=null;
	    	while (tokenizer == null || !tokenizer.hasMoreTokens()) {
	            try {
	              fullLine=reader.readLine();
	            } catch (IOException e) {
	              throw new RuntimeException(e);
	            }
	            return fullLine;
	          }
	          return fullLine;
	    }
		public String next() {
	      while (tokenizer == null || !tokenizer.hasMoreTokens()) {
	        try {
	          tokenizer = new StringTokenizer(reader.readLine());
	        } catch (IOException e) {
	          throw new RuntimeException(e);
	        }
	      }
	      return tokenizer.nextToken();
	    }
		public long nextLong() {
		      return Long.parseLong(next());
		    }
	    public int nextInt() {
	      return Integer.parseInt(next());
	    }
	  }
	
	public static HashMap<Integer,Long> getcatalan(int n){
		HashMap<Integer,Long> a=new HashMap<Integer,Long>();
		a.put(0,(long)1);
		for(int i=1;i<=n+1;i++){
			long m=2*(2*i-1);
			long m1=m*a.get(i-1);
			long m3=m1/(i+1);
			//out.println(m+" "+m1+" "+m2+" "+m3);
			
			a.put(i,m3%1000000007);
		}
		return a;
	}
	
	public static int getGdc(int[] x) {
	    // get the smallest of all number no need to check for higher values
	    int smallest = getSmallest(x);

	    for(int i = smallest; i >= 1; i--) {
	       int j;
	       for(j = 0; j < x.length; ++j) {
	           if(x[j] % i != 0)
	               break;
	       }
	       // if we pass through the array with all % == 0 return the value
	       if(j == x.length)
	           return i;
	    }
	    // so the only possible is 1
	    return 1;
	}

	// return smallest number of an array of int
	public static int getSmallest(int[] x) {
	    int smallest = x[0];
	    for(int i = 1; i < x.length; ++i) {
	        if(x[i] < smallest)
	            smallest = x[i];
	    }
	    return smallest;
	}
	public static long gcd(long number1, long number2) {  
		if(number2 == 0){
			return number1;
		} 
		return gcd(number2, number1%number2); 
	}
	
	public static void extendedEuclidean(long a,long b){
		if(b == 0) {
	        d = a;
	        x = 1;
	        y = 0;
	    }
	    else {
	        extendedEuclidean(b, a%b);
	        long temp = x;
	        x = y;
	        y = temp - (a/b)*y;
	    }
	}
	
	public static int combinations(int n,int r){
		if(n==r) return 1;
		if(r==1) return n;
		if(r==0) return 1;
		return combinations(n-1,r)+ combinations(n-1,r-1);
	}
	public static long binomialCoeff(int n, int k)
	{
	    long C[][]= new long[n+1][k+1];
	    int i, j;
	 
	    // Caculate value of Binomial Coefficient in bottom up manner
	    for (i = 0; i <= n; i++)
	    {
	        for (j = 0; j <= Math.min(i, k); j++)
	        {
	            // Base Cases
	            if (j == 0 || j == i)
	                C[i][j] = 1;
	 
	            // Calculate value using previosly stored values
	            else
	                C[i][j] = C[i-1][j-1] + C[i-1][j];
	        }
	    }
	 
	    return C[n][k];
	}
	public static long expo(long a, long b){
	    if (b==1)
	        return a%mod;
	    if (b==2)
	        return (a%mod)*(a%mod);

	    if (b%2==0){
	            return expo(expo(a%mod,(b%mod)/2),2);
	    }
	    else{
	        return a*(expo(expo(a%mod,((b%mod-1%mod)%mod)/2),2));
	    }
	}
	
	public static int[] sieve(int N){
		int arr[]= new int[N+1];
		int b[]=new int[N+1];
		for(int i=2;i<Math.sqrt(N);i++){
			if(arr[i]==0){
				
				for(int j= i*i;j<= N;j= j+i){
					arr[j]=1;
				}
			}
		}
		return arr;
		// All the i for which arr[i]==0 are prime numbers.
	}
	static class Pair implements Comparable<Pair>
    {
        int f,s;
        Pair(int ii, int cc)
        {
            f=ii;
            s=cc;
        }
        
        public int compareTo(Pair o) 
        {
            return Integer.compare(this.f, o.f);
        }
        
    }
	public static class company{
		public int t;
		public int d;
		public company(int m,int f){
			this.t=m;
			this.d=f;
		}
		public int get_t(){
			return this.t;
		}
		public int get_d(){
			return this.d;
		}
	}
	public static class pair_comparator implements Comparator<company>{

		@Override
		public int compare(company arg0, company arg1) {
			// TODO Auto-generated method stub
			return arg0.t-arg1.t;
		}
		
	}

}