Given the task definition and input, reply with output. 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: Robert decided to make a sandwich. Sentence2: He got the bread and bologna and cheese. Sentence3: He started to make the sandwich but forgot the mayo, so he got that. Sentence4: He put the bologna and cheese and mayo between two pieces of bread. Sentence5: Robert ate his sandwich.
Robert