#include <bits/stdc++.h>
using namespace std;
int n, m;
string res[101];
int dx[] = {0, 0, -1, 1};
int dy[] = {-1, 1, 0, 0};
inline bool in(int x, int y) {
  if (x < 0 || y < 0 || x >= n || y >= m) return 0;
  return 1;
}
int main(int argc, char **argv) {
  cin >> n >> m;
  for (int i = 0; i <= n - 1; i++) {
    cin >> res[i];
  }
  int c = 1;
  for (int i = 0; i <= n - 1; i++) {
    c = i % 2;
    for (int j = 0; j <= m - 1; j++) {
      if (res[i][j] == '.') {
        if (c)
          res[i][j] = 'B';
        else
          res[i][j] = 'W';
      }
      if (c == 1)
        c = 0;
      else
        c = 1;
    }
  }
  for (int i = 0; i <= n - 1; i++) cout << res[i] << "\n";
  return 0;
}
