import java.util.Scanner;

public class Main {
	static int t, p;
	static char[][] b;
	static int[] numYRow, numYCol, numYRowCurr, numYColCurr;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		t = sc.nextInt();
		p = sc.nextInt();
		StringBuffer s = new StringBuffer();
		while(t!=0 && p!=0)
		{
			b = new char[t][p];
			/*for(int i=0; i<t; i++)
			{
				for(int j=0; j<p; j++)
				{
					b[i][j] = 'Y';
				}
			}*/
			numYRow = new int[t];
			numYCol = new int[p];
			numYRowCurr = new int[t];
			numYColCurr = new int[p];
			for(int i=0; i<t; i++)
			{
				numYRow[i] = sc.nextInt();
				//numYRowCurr[i] = p;
			}
			for(int i=0; i<p; i++)
			{
				numYCol[i] = sc.nextInt();
				//numYColCurr[i] = t;
			}

			boolean solved = solve(0);

			if(solved)
			{
				for(int i=0; i<t; i++)
				{
					for(int j=0; j<p; j++)
					{
						s.append(b[i][j]);
					}
					s.append("\n");
				}
				s.append("\n");
			}
			else
				s.append("Impossible\n\n");
			t = sc.nextInt();
			p = sc.nextInt();
		}
		System.out.println(s.substring(0,s.length()-1));
	}

	static boolean solve(int val){
		int i=val/p;
		int j=val%p;
		if(val==t*p)
		{
			return true;
		}
		if(numYRowCurr[i]+p-j-1>=numYRow[i]&&numYColCurr[j]+t-i-1>=numYCol[j])
		{
			b[i][j] = 'N';
			if(solve(val+1)) return true;
		}
		if(numYRowCurr[i]+1<=numYRow[i]&&numYColCurr[j]+1<=numYCol[j])
		{
			numYRowCurr[i]++;
			numYColCurr[j]++;
			b[i][j] = 'Y';
			if (solve(val+1)) return true;
		}

		return false;
	}
}