#include "bits/stdc++.h"
using namespace std;
int f[11][11];
int tileNumber = 0;
char symbol(int x) {
if (x == -2) return '.';
if (x == -1) return '@';
if (x < 26) return 'a' + x;
return 'A' + x - 26;
}
void verticalTile(int x, int y)
{
f[x][y] = tileNumber;
f[x + 1][y] = tileNumber;
++tileNumber;
}
void horizontalTile(int x, int y)
{
f[x][y] = tileNumber;
f[x][y + 1] = tileNumber;
++tileNumber;
}
void tile(int x1, int y1, int x2, int y2)
{
if ((x2 < x1) || (y2 < y1)) return;
if ((x2 - x1) % 2 != 0) { //vertical tiling
for (int i = x1; i < x2; i += 2) {
for (int j = y1; j <= y2; ++j) {
verticalTile(i, j);
}
}
return;
}
if ((y2 - y1) % 2 != 0) { //horizontal tiling
for (int i = x1; i <= x2; ++i) {
for (int j = y1; j < y2; j += 2) {
horizontalTile(i, j);
}
}
return;
}
}
int main()
{
int n, m, x, y;
cin >> n >> m >> x >> y;
--n; --m; --x; --y;
f[x][y] = -1;
int left = y - 1 - (y & 1);
int right = y + 1 + ((m - y) & 1);
int top = x - 1 - (x & 1);
int bottom = x + 1 + ((n - x) & 1);
tile(0, 0, n, left);
tile(0, right, n, m);
tile(0, left + 1, top, right - 1);
tile(bottom, left + 1, n, right - 1);
if (right - left == 4 && bottom - top == 4) {
//3x3
verticalTile(top + 1, left + 1);
verticalTile(top + 2, left + 3);
horizontalTile(top + 1, left + 2);
horizontalTile(top + 3, left + 1);
}
else if (right - left == 2 && bottom - top == 2) {
//1x1
}
else {
cout << "-1" << endl;
return 0;
}
for (int i = 0; i <= n; ++i)
{
for (int j = 0; j <= m; ++j)
{
cout << symbol(f[i][j]);
}
cout << endl;
}
return 0;
}
