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
    //    A Computer is Like a mischievous genie.
    //    It will give you exactly what you ask for,
    //    but not always what you want
    //    A code by Rahul Verma


    import java.io.BufferedOutputStream;
    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.io.PrintWriter;
    import java.math.BigInteger;
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.Collections;
    import java.util.Comparator;
    import java.util.HashMap;
    import java.util.HashSet;
    import java.util.LinkedHashSet;
    import java.util.LinkedList;
    import java.util.List;
    import java.util.PriorityQueue;
    import java.util.Queue;
    import java.util.Set;
    import java.util.Stack;
    import java.util.StringTokenizer;
    import java.util.TreeMap;



    public class Main {


        static class Clock {

            protected long start, stop;

            public void start() {

                start = System.currentTimeMillis();
            }

            public void stop() {
                stop = System.currentTimeMillis();
            }

            public String getTime() {

                return ((stop - start) + " ms");
            }
        }


        public static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));

        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[] nextSArray() {
                String sr[] = null;
                try {
                    sr = br.readLine().trim().split(" ");
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return sr;
            }

            String nextLine() {
                String str = "";
                try {
                    str = br.readLine();
                } catch (IOException e) {
                    e.printStackTrace();
                }

                return str;
            }
        }


        static long powmodulo(long a, long p) {
            if (p == 0) {
                return 1 % mod;
            }
            if (p == 1) {
                return a % mod;
            }
            long ans = 1;
            while (p > 0) {
                if ((p & 1) > 0) {
                    ans = (ans * a) % mod;
                }
                a = (a * a) % mod;
                p = p >> 1;
            }
            return ans % mod;
        }


        static long mod = 1000000007;

        static long gcd(long a, long b) {
            if (a == 0) {
                return b;
            }
            return gcd(b % a, a);
        }

        static long fast_powerNumbers(long a, long n) {
            if (n == 1) {
                return a;
            }
            long ans = fast_powerNumbers(a, n / 2);
            if (n % 2 == 0) {
                return (ans * ans);
            } else {
                return ((ans * ans) * (a));
            }
        }


        static void dfs_helper(int[][] arr, int i, int j, int team, int n, int m) {
            arr[i][j] = team;
            if (i - 1 >= 0 && arr[i - 1][j] == 1) {
                dfs(arr, i - 1, j, team, n, m);
            }
            if (j - 1 >= 0 && arr[i][j - 1] == 1) {
                dfs(arr, i, j - 1, team, n, m);
            }
            if (i + 1 < n && arr[i + 1][j] == 1) {
                dfs(arr, i + 1, j, team, n, m);
            }
            if (j + 1 < m && arr[i][j + 1] == 1) {
                dfs(arr, i, j + 1, team, n, m);
            }

        }

        static void dfs(int[][] arr, int i, int j, int team, int n, int m) {
            dfs_helper(arr, i, j, team, n, m);

        }
        public static int arr[];


        static void seive(int n) {
            // 1 is not prime
            arr = new int[n + 1];
            arr[0] = arr[1] = 1;
            for (int i = 4; i <= n; i = i + 2) {
                arr[i] = 1;
            }
            for (int i = 3; i * i <= n; i = i + 2) {
                if (arr[i] == 0) {
                    for (int j = i * i; j <= n; j = j + i) {
                        arr[j] = 1;
                    }

                }
            }
        }




        public static void main(String[] args) throws Exception {
            FastReader sc = new FastReader();

            Clock clock = new Clock();

            clock.start();
            int n= sc.nextInt();
            int k= sc.nextInt();
            int a= sc.nextInt();
            int b= sc.nextInt();
            StringBuilder ans=new StringBuilder();
            int c=0;
            int last=0;
            boolean found =true;
            while(a+b!=0)
            {
              if(last==0)
              {
                  if(a>b)
                  {
                      for (int i = 0; i < k && a>0; i++) {
                                    ans.append("G");
                                    --a;
                     }
                      last=1;
                  }
                  else
                  {
                      for (int i = 0; i < k && b>0; i++) {
                          ans.append("B");
                          --b;
                      }
                      last=2;
                  }
              }
              else if(last==1)
              {
                  if(b==0)
                  {
                      found=false;
                      break;
                  }
                  int m=1;
                  if(b>a)
                      m=k;
                  for (int i = 0; i < m && b>0; i++) {
                      ans.append("B");
                      --b;
                  }
                  last=2;

              }
              else
              {
                  if(a==0)
                  {
                      found=false;
                      break;
                  }
                  int m=1;
                  if(a>b)
                      m=k;
                  for (int i = 0; i < m && a>0; i++) {
                      ans.append("G");
                      --a;
                  }
                  last=1;
              }
            }
            if(found)
            {
                System.out.println(ans);
            }
            else
            {
                System.out.println("NO");
                //System.out.println(ans);
            }



        }
    }


    class Pair{

        int a,b;
        Pair(int a,int b)
        {
            this.a=a;
            this.b=b;
        }
    }
    class DSU
    {
        int parent[];
        int rank[];

        long sum[] ;
        DSU(int n)
        {
            this.parent=new int[n];
            this.rank=new int[n];
            sum=new long[n];
            Arrays.fill(parent,-1);
            Arrays.fill(rank,1);

        }

        int find(int s1)
        {
            if(parent[s1]==-1)
                return s1;
            return parent[s1]=find(parent[s1]);
        }

        void unite(int s1,int s2)
        {
            int p1=this.find(s1);
            int p2=this.find(s2);
            if(p1==p2)
                return;
            if(rank[p1]>rank[p2])
            {
                parent[p2]=p1;
                rank[p1]+=rank[p2];
                // System.out.println(arr[p2]);

                sum[p1]+=sum[p2];
                //sum[p2]+=sum[p1];

            }
            else
            {
                parent[p1]=p2;
                rank[p2]+=rank[p1];
                //System.out.println(arr[p1]);
                sum[p2]+=sum[p1];
                //sum[p1]+=sum[p2];
            }
        }


    }

    class Gaph {

        HashMap<Integer, ArrayList<Integer>> hm;

        Gaph() {
            hm = new HashMap<>();
        }

        Gaph(int n) {

            hm = new HashMap<>();
            for (int i = 0; i < n; i++) {
                hm.put(i, new ArrayList<Integer>());
            }
        }

        // function for adding an edge.................................................
        public void addEdge(int a, int b, boolean isDir) {
            if (isDir) {
                if (hm.containsKey(a)) {
                    hm.get(a).add(b);
                } else {
                    hm.put(a, new ArrayList<>(Arrays.asList(b)));
                }
            } else {
                if (hm.containsKey(a)) {
                    hm.get(a).add(b);
                } else if (!hm.containsKey(a)) {
                    hm.put(a, new ArrayList<>(Arrays.asList(b)));
                }

                if (hm.containsKey(b)) {
                    hm.get(b).add(a);
                } else if (!hm.containsKey(b)) {
                    hm.put(b, new ArrayList<>(Arrays.asList(a)));
                }
            }
        }


    }

    // out.println(al.toString().replaceAll("[\\[|\\]|,]",""));