#include<bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using ull = unsigned long long;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;

#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mp make_pair
#define ins insert
#define btpc __builtin_popcount
#define btclz __builtin_clz

#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};

template<class X, class Y>
    bool minimize(X &x, const Y &y) {
        if (x > y)
        {
            x = y;
            return true;
        }
        return false;
    }
template<class X, class Y>
    bool maximize(X &x, const Y &y) {
        if (x < y)
        {
            x = y;
            return true;
        }
        return false;
    }

const int MOD = 1e9 + 7; //998244353

template<class X, class Y>
    void add(X &x, const Y &y) {
        x = (x + y);
        if(x >= MOD) x -= MOD;
    }

template<class X, class Y>
    void sub(X &x, const Y &y) {
        x = (x - y);
        if(x < 0) x += MOD;
    }

/* Author : Le Ngoc Bao Anh, 11A5, LQD High School for Gifted Student*/

const ll INF = 1e9;
const int N = 1e5 + 10;

int a[30][30], b[30][30], state[30];
int dp[(1 << 22) + 10];

void solve() {
    int n, m;
    cin >> n >> m;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            char c; cin >> c;
            a[i][j] = (c == 'X' ? 1 : 0);
        }
    }

    auto turn = [&](int i, int j) -> void {
        b[i][j] ^= 1;
        if(i > 1) b[i - 1][j] ^= 1;
        if(j > 1) b[i][j - 1] ^= 1;
        if(i < n) b[i + 1][j] ^= 1;
        if(j < m) b[i][j + 1] ^= 1;
    };

    auto calc = [&](int msk) -> pii {
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= m; j++) b[i][j] = a[i][j];
        }

        int steps = 0;
        for(int i = 0; i < n; i++) {
            if(msk >> i & 1) {
                turn(i + 1, 1);
                steps++;
            }
        }

        for(int j = 2; j <= m; j++) {
            for(int i = 1; i <= n; i++) {
                if(b[i][j - 1]) {
                    turn(i, j);
                    steps++;
                }
            }
        }

        int ans = 0;
        for(int i = 1; i <= n; i++) {
            if(b[i][m]) ans |= (1 << (i - 1));
        }

        return mp(ans, steps);
    };

    int ans = INF;
    pii g = calc(0);
    dp[0] = g.fi;
    if(g.fi == 0) minimize(ans, g.se);

    for(int i = 0; i < n; i++) {
        dp[1 << i] = calc(1 << i).fi;
        state[i] = dp[1 << i] ^ dp[0];
    }

    for(int msk = 1; msk < (1 << n); msk++) {
        for(int i = 0; i < n; i++) {
            if(msk >> i & 1) {
                dp[msk] = dp[msk ^ (1 << i)] ^ state[i];
                break;
            }
        }

        if(dp[msk] == 0) minimize(ans, calc(msk).se);
    }

    if(ans == INF) {
        cout << "Damaged billboard.";
        return;
    }

    cout << "You have to tap " << ans << " tiles.";
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #else
    //online
    freopen("billboard.inp", "r", stdin);
    freopen("billboard.out", "w", stdout);
    #endif

    int tc = 1, ddd = 0;
    // cin >> tc;
    while(tc--) {
        //ddd++;
        //cout << "Case #" << ddd << ": ";
        solve();
    }
}