import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Solution to Checkerboard
 * 
 * @author vanb
 */
public class checkerboard_vanb
{
    /** Input. */
    private static Scanner sc;
    
    /** Output. */
    private static PrintStream ps;
    
    /**
     * Do it!
     */
    private void doit()
    {
        int r = sc.nextInt();
        int c = sc.nextInt();
        int v = sc.nextInt();
        int h = sc.nextInt();
        
        int as[] = new int[v];
        for( int i=0; i<v; i++ ) as[i] = sc.nextInt();
        
        int bs[] = new int[h];
        for( int i=0; i<h; i++ ) bs[i] = sc.nextInt();
        
        char board[][] = new char[r][];
        char rowa[] = new char[c];
        char rowb[] = new char[c];
        char squarea = 'B';
        char squareb = 'W';
        
        int k=0;
        for( int i=0; i<h; i++ )
        {
            for( int j=0; j<bs[i]; j++ ) 
            {
                rowa[k] = squarea;
                rowb[k] = squareb;
                ++k;
            }
            char temp = squarea;
            squarea = squareb;
            squareb = temp;
        }
        
        k=0;
        for( int i=0; i<v; i++ )
        {
            for( int j=0; j<as[i]; j++ )  board[k++] = rowa;
            char temp[] = rowa;
            rowa = rowb;
            rowb = temp;
        }
        
        for( char row[] : board ) ps.println( new String(row) );
        
    }
        
    /**
     * Main.
     * 
     * @param args unused
     * @throws Exception
     */
    public static void main( String[] args ) throws Exception
    {
        sc = new Scanner( System.in );
        ps = System.out;
        
        new checkerboard_vanb().doit();
    }

}