In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.

Sentence1: Riley had always enjoyed playing board games. Sentence2: One day he decides to play chess with a friend. Sentence3: It was a difficult game. Sentence4: In the end, Riley lost the chess game. Sentence5: However, he still loved board games.
A friend, Riley

Sentence1: Charles rented a room in May's house. Sentence2: One day, Charles had an urge to try his luck in Vegas. Sentence3: He was very lucky at dice, making six thousand his first night. Sentence4: He stayed in Vegas for two weeks, gambling, making $80,000. Sentence5: He came home and someone was in his place, May rented his room out.
May, Someone, Charles

Sentence1: Isaac was prone to bouts of depression. Sentence2: He never made many friends, and was usually found by himself. Sentence3: He imagined that no one would miss him and began to cry. Sentence4: His mother heard his sobbing and came to find out what was wrong. Sentence5: She encouraged him that she would miss him if he disappeared.
Isaac, Friends, Mother