Calculate the number 300

An out-of-work actor gets a call from his agent one day. "I’ve got you a job," says his agent. "That’s great," says the actor, what is it?" "Well," says his agent, "it’s a one-liner" "That’s okay," replies the actor, "I’ve been out of work for so long I’ll take anything. What’s the line?" "Hark, I hear the cannons roar" says the agent. "I love it" says the actor "When’s the audition?" "Wednesday" says the agent.

Wednesday comes and the actor arrives at the audition. He marches on stage and shouts: "Hark, I hear the cannons roar". "Brilliant," says the director, "you’ve got the job. Be here 9 o’clock Saturday evening."

The actor is so happy he got the job that he goes on a major bender. He wakes up at 8:30 Saturday evening and runs to the theatre continually repeating his line; "Hark, I hear the cannons roar, hark, I hear the cannons roar, hark, I hear the cannons roar."

He arrives at the stage entrance, out of breath and is stopped by the guard. "Who the hell are you?" asks the guard. "I’m "hark, I hear the cannons roar." "If you’re "hark I hear the cannons roar", you’re late. Get up to makeup right now!"

So he runs up to makeup. "Who the hell are you" asks the makeup girl. "I’m "hark I hear the cannons roar."" "If you’re hark I hear the cannons roar", you’re late. Sit down here." And she applies the makeup. "Now quick, get down to the stage, you’re about to go on."

He dashes down to the stage. "Who the hell are you?" asks the stage manager. "I’m "hark, I hear the cannons roar."" "You’re "hark, I hear the cannons roar?" Get out there, the curtain’s about to go up."

He tears onto the stage. The curtains rise, the house is full. 

Suddenly there is an almighty bang behind him, and the actor shouts "WHAT THE FUCK WAS THAT?"