#include <iostream>
#include <vector>
using namespace std;

typedef vector<char> Fila;
typedef vector<Fila> Matriu;

void escriu(const Matriu& M) {
    int n = M.size();
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) cout << M[i][j];
        cout << endl;
    }
    cout << endl;
}

//Per mirar els basteris adjacents, fem una funcio que ens indiqui
//si la posicio es troba fora de la matriu.
bool fora_matriu(const Matriu& M, int f, int c) {
    int n = M.size();
    return (f < 0 or f >= n or c < 0 or c >= n);
}

int bacteris_adjacents (const Matriu& M, int f, int c) {
    int cont_bacteris = 0;
    for (int i = f-1 ; i <= f+1; ++i) {
        for (int j = c-1; j <= c+1; ++j) {
            if (not fora_matriu(M,i,j)) {
                if (M[i][j] == 'B') ++cont_bacteris;
            }
        }
    }
    if (M[f][c] == 'B') --cont_bacteris;
    return cont_bacteris;
}

void desenvolupa_joc_vida(Matriu& M, bool& canvi, int& i, int& j) {
    if (M[i][j] == '.' and bacteris_adjacents(M,i,j) == 3) {
        M[i][j]= 'B';
        canvi = true;
    }
    else if (M[i][j] == 'B' and bacteris_adjacents(M,i,j) < 2) {
        M[i][j]= '.';
        canvi = true;
    }
}

void fer_volta(Matriu& M, int v, bool& canvi) {
    if (canvi and v != 0) {
        int n = M.size();
        canvi = false;
        for (int j = 0; j < n; ++j) {
            if (j%2 == 0) {
                for (int i = 0; i < n; ++i) {
                    desenvolupa_joc_vida(M,canvi,i,j);
                }
            }
            else {
                for (int k = n-1; k >= 0; --k) {
                    desenvolupa_joc_vida(M,canvi,k,j);
                }
            }
        }
        escriu(M);
        fer_volta(M,v-1,canvi);
    }
}

int main() {
    int n;
    cin >> n;
    Matriu M(n, vector<char>(n,'.'));
    int v;
    cin >> v;
    int f, c;
    while (cin >> f >> c) M[f][c] = 'B';
    escriu(M);
    bool canvi = true;
    fer_volta(M,v,canvi);
}