#include <bits/stdc++.h>
using namespace std;

signed main(){
  int W, H; cin >> W >> H;
  string col; cin >> col;
  for( int i = 0, p = 0; i < H; ++i )
    for( int j = 0; j < W; ++j, cout << endl )
      cout << ( p & 1 ? ( col == "W" ? "B" : "W" ) : col );
  return 0;
}