#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int w, h;
    string c;
    cin >> w >> h >> c;
    if(c[0] == 'B')c += 'W';
    else c += 'B';
    rep(i,h){
        rep(j,w){
            cout << c[(i + j) % 2];
        }
        cout << endl;
    }
    return 0;
}