#include <bits/stdc++.h>

using namespace std;

int main() {
    int h, w, fill;
    char c;

    cin >> h >> w >> c >> fill;

    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            if (j == 0 || j == w - 1 || i == 0 || i == h - 1)
                cout << c;
            else if (fill) {
                cout << c;
            } else {
                cout << ' ';
            }
        }
        cout << endl;
    }

    return 0;
}