A_s = \{\bigcup_{i=1}^s a_i | a_i \in A\}

A_s = \{\bigcup_{i=1}^s a_i | a_i \in A\}

A_s = \{\bigcup_{i=1}^s a_i | a_i \in A\}

A_s = \{\bigcup_{i=1}^s a_i | a_i \in A\}