package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	var n, m int
	fmt.Fscan(in, &n, &m)

	board := make([][]byte, n)
	for i := 0; i < n; i++ {
		var s string
		fmt.Fscan(in, &s)
		row := []byte(s)
		for j := 0; j < m; j++ {
			if row[j] == '.' {
				if (i+j)%2 == 0 {
					row[j] = 'B'
				} else {
					row[j] = 'W'
				}
			}
		}
		board[i] = row
	}

	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()
	for i := 0; i < n; i++ {
		fmt.Fprintln(out, string(board[i]))
	}
}