#include <cstdio>
#include <vector>
#include <set>
#include <map>
#include <string>
#include <iostream>
#define SIZE(x) ((int) (x).size())
#define REP(i, n) for (int i = 0; i < (int) (n); ++i)
using namespace std;

#define MAXN 107

typedef pair<int, int> PI;

int n, m;
char B[MAXN][MAXN];
char R[MAXN][MAXN];

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

PI DFS1(int y, int x, bool parity) {
	R[y][x] = 'v';
	PI res = PI(parity, !parity);
	REP(d, 4) {
		int ny = y + dy[d];
		int nx = x + dx[d];
		if (0 <= ny && ny < n && 0 <= nx && nx < m && R[ny][nx] == '?') {
			PI t = DFS1(ny, nx, !parity);
			res.first += t.first;
			res.second += t.second;
		}
	}
	return res;
}

void DFS_same(int y, int x) {
	R[y][x] = 'A';
	REP(d, 4) {
		int ny = y + dy[d];
		int nx = x + dx[d];
		if (0 <= ny && ny < n && 0 <= nx && nx < m && R[ny][nx] == 'v') {
			DFS_same(ny, nx);
		}
	}
}

void DFS_chess(int y, int x, bool parity) {
	R[y][x] = (!parity) ? 'B' : 'A';
	REP(d, 4) {
		int ny = y + dy[d];
		int nx = x + dx[d];
		if (0 <= ny && ny < n && 0 <= nx && nx < m && R[ny][nx] == 'v') {
			DFS_chess(ny, nx, !parity);
		}
	}
}

int main() {
	while (scanf("%d%d", &n, &m), n) {
		REP(i, n)
			scanf("%s", B[i]);
		REP(i, n) REP(j, m)
			if (B[i][j] == 'X')
				R[i][j] = 'X';
			else
				R[i][j] = '?';
		REP(i, n) REP(j, m)
			if (R[i][j] == '?') {
				PI x = DFS1(i, j, false);
				if (x.first == x.second) {
					DFS_same(i, j);
				} else {
					if (x.first > x.second)
						DFS_chess(i, j, true);
					else
						DFS_chess(i, j, false);
				}
			}

		REP(i, n) {
			REP(j, n)
				putchar(R[i][j]);
			putchar('\n');
		}
		putchar('\n');
	}
}