What did Neil Armstrong really say when he took his first step on the moon?

Millions on Earth who listened to him on TV or radio heard this :

"That's one small step for man, one giant leap for mankind."

But after returning from space, Armstrong said that wasn't what he had planned to say. He said there was a lost word in his famous one-liner from the moon: "That's one small step for 'a' man." It's just that people just didn't hear it."