package com.bakes;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;

public class A {
    public static void main(String[] args) {
        A park = new A();
        park.calculate();

    }

    private void calculate() {
        BufferedReader in;
        String strLine1;
        String strLine2;
        String strLine3;
        PrintWriter out;
        try {
            in = new BufferedReader(new FileReader("input.in"));
            in.readLine();
            FileWriter outFile = new FileWriter("output.txt");
            out = new PrintWriter(outFile);
            int n = 0;

            while ((strLine1 = in.readLine()) != null) {
                n++;

                String[] data = strLine1.split(" ");
                System.out.println(strLine1);
                int height = Integer.parseInt(data[0]);
                int width = Integer.parseInt(data[1]);
                char[][] image = new char[height][width];
                for (int i = 0; i<height; i++)
                {
                    char[] line = in.readLine().toCharArray();
                    for (int j = 0; j < width; j++)
                    {
                            image[i][j] = line[j];
                    }
                }

                for (int i = 0; i<height-1; i++)
                {
                    for (int j = 0; j < width-1; j++)
                    {
                        if ((image[i][j] == '#') && (image[i][j+1] == '#') && (image[i+1][j] == '#') && (image[i+1][j+1] == '#'))
                        {
                            image[i][j] = '/';
                            image[i][j+1] = '\\';
                            image[i+1][j] = '\\';
                            image[i+1][j+1] = '/';
                        }
                    }
                }

                boolean done = true;
                for (int i = 0; i<height; i++)
                {
                    for (int j = 0; j < width; j++)
                    {
                        if (image[i][j] == '#')
                        {
                            done = false;
                        }
                    }
                }
                out.println("Case #"+n+":");
                if (!done)
                {
                    out.println("Impossible");
                }
                else if (true)
                {
                    for (int i = 0; i<height; i++)
                    {
                        String s = "";
                        for (int j = 0; j < width; j++)
                        {
                            s += image[i][j];
                        }
                        out.println(s);

                    }
                }
            }
            out.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}