protected void createNullMark() {
Matrix m = marks();
Random rnd = new Random();
int x = rnd.nextInt(m.columns());
int y = rnd.nextInt(m.rows());
AddNullMark(x, y);
}
protected void createBlockMark() {
Matrix m = marks();
Random rnd = new Random();
int x = rnd.nextInt(m.columns());
int y = rnd.nextInt(m.rows());
while (!blockMark(x, y)) ;
}
