#include <algorithm>
#include <iostream>
#include <iomanip>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <cmath>
using namespace std;

#define FOR(i,s,e) for (int i = int(s); i < int(e); i++)
#define FORIT(i,c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); i++)
#define ISEQ(c) (c).begin(), (c).end()

int main(){
	int W,H;
	cin >> W >> H;
	string C;
	cin >> C;

	FOR(i,0,H){
		FOR(j,0,W){
			if(i%2 == 0){
				if(C == "B" && j%2 == 0) cout << "B";
				else if(C == "B" && j%2 != 0) cout << "W";
				else if(j%2 == 0) cout << "W";
				else cout << "B";
			}else{
				if(C == "B" && j%2 == 0) cout << "W";
				else if(C == "B" && j%2 != 0) cout << "B";
				else if(j%2 == 0) cout << "B";
				else cout << "W";
			}
		}
		cout << endl;
	}
	return 0;
}