import java.util.$*$; public class Test $\{$

public static void main$($String$[]$ args$)\{$ Set set $=$ new HashSet$()$; set.add$($new A$())$;

set.add$($new A$())$;

set.add$($new A$())$; set.add$($new A$())$; System.out.println$($set$)$;

$\}\}$

class A $\{$ int r $=1$;

public String toString$()\{$ return r $+""$;

$\}$

public boolean equals$($Object o$)\{$ return this.r $==(($A$)$o$).$r;

$\}$

public int hashCode$()\{$ return r;

$\}\}$

a$.[1]$

b$.[1,1]$

c$.[1,1,1]$

d$.[1,1,1,1]$