using System;
 
public class Test
{
  public static void Main()
  {
    Random ran = new Random();
 
    int n = 4, m = 5;
    int?[,] a = new int?[n, m];
 
    for (int q=0; q<n; ++q)
      for (int w=0; w<m; ++w)
        a[q, w] = ran.Next(0, 9);
 
    a[2, 3] = null;
 
    for (int q=0; q<n; ++q)
    {
      for (int w=0; w<m; ++w)
        Console.Write("{0} ", a[q, w]?.ToString() ?? ".");
 
      Console.WriteLine();
    }
  }
}

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