#include <vector>
#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <cstring>

#define SZ(x) ((int)(x).size())

using namespace std;

int r,c;

vector<string> bill;

int value(char c){
	if ( c == 'X' ) return 1;
	return 0;
}

vector<int> s;
vector<int> slob;
int mat[257][257];
int cb;

void zamjeni(int x, int y){
	register int t;
	for ( register int i = 0; i < r * c + 1; i++){
		t = mat[x][i];
		mat[x][i] = mat[y][i];
		mat[y][i] = t;
	}		
}

void descent(int depth){
	if ( depth == SZ(slob) ){
		int ret = 0;
		for (int i = 0; i < r * c; i++){
			if ( mat[i][i] == 1 ){
				int t = mat[i][r * c];
				for (int j = 0; j < SZ(slob); j++)
					if ( s[j] && mat[i][slob[j]] )
						t=t^1;
				if ( t ) ret++;
			}
			if ( ret > cb ) break;
		}
		cb = ret;
	}
	else {
		s[depth] = 1;
		descent(depth + 1);
		s[depth] = 0;
		descent(depth + 1);
	}
}

int main(){
	while(1){
		scanf("%d %d\n", &r, &c);
		if (!r && !c) break;

		bill.clear();
		for (int i = 0; i < r; i++){
			char buff[100];
			gets(buff);
			bill.push_back(string(buff));			
		}


		memset(mat, 0, sizeof(mat));

		for (int i = 0; i < r; i++){
			for (int j = 0; j < c; j++){
				mat[i * c + j][r * c] = value(bill[i][j]);
				mat[i * c + j][i * c + j] = 1;
				if ( i > 0 )
					mat[i * c + j][(i - 1) * c + j] = 1;
				if ( j > 0 )
					mat[i * c + j][i * c + j - 1] = 1;
				if ( i + 1 < r )
					mat[i * c + j][(i + 1) * c + j] = 1;
				if ( j + 1 < c )
					mat[i * c + j][i * c + j + 1] = 1;					
			}
		}

		for (int i = 0; i < r * c; i++){
			if ( !mat[i][i] ){
				for (int j = i + 1; j < r * c; j++)
					if ( mat[j][i] ){
						zamjeni(i, j);
						break;
					}
			}

			for (int j = 0; j < r * c; j++)
				if ( j != i && mat[j][i] )
					for (int k = 0; k < r * c + 1; k++)
						mat[j][k] = mat[j][k] ^ mat[i][k];
		}

		int ret = 0;
		slob.clear();
		for (int i = 0; i < r * c && ret != -1; i++){
			if ( mat[i][r * c] ) ret++;

			int cnt = 0;
			for (int j = 0; j < r * c + 1 - 1; j++)
				cnt += mat[i][j];

			if ( !cnt ){
				slob.push_back(i);
				s.push_back(-1);
			}
			if ( !cnt && mat[i][r * c] ) ret = -1;
		}

		if ( ret == -1 ) {
			printf("Damaged billboard.\n");
			continue;
		}

		cb = ret;
		descent(0);
		ret = cb;
		
		if ( ret != -1) printf("You have to tap %d tiles.\n", ret);
	}
}