A man is driving down the road and breaks down near a monastery. He goes to the monastery, knocks on the door, and says, "My car broke down. Do you think I could stay the night?"
The monks graciously accept him, feed him dinner, and even fix his car. As the man falls asleep that night, he hears a strange sound. The next morning, he asks the monks what the sound was.
"We can't tell you. You're not a monk" they respond.
The man is disappointed but thanks them anyway and continues on his trip.
Several years later the same man breaks down in front of the same monastery. The monks again accept him, feed him, and even fix his car. That night, he hears the same strange noise that he had heard years earlier.
The next morning he again asks what it is, and again the monks reply, "We can't tell you. You're not a monk."
The man says, "All right, all right. I'm dying to know. If the only way I can find out the source of that sound is to become a monk, tell me how do I become a monk?"
"You must travel the earth and tell us how many blades of grass there are and the exact number of sand pebbles. When you find these numbers, you will become a monk," they reply.
The man sets about his task. Many years later he returns and knocks on the door of the monastery. "I have traveled the earth and have found what you asked for. There are 145,236,284,232 blades of grass and 231,281,219,999,129,382 sand pebbles on the earth."
"Congratulations!" the monks reply. "You are now a monk. We will now show you the way to the sound."
The monks proceed to lead the man to a wooden door, where the head monk says, "The sound is behind that door."
The man reaches for the knob, but cannot open it because the door is locked.
"Really funny," he says, "May I have the key please?"
The monks give him the key and he opens the door. Behind the wooden door is another door made of stone. The monks give him the key to this door too, and he opens it-only to find a door made of ruby. He asks for, and receives another key from the monks. But behind that door is another door, this one made of sapphire. On and on this went until the man had gone through doors of emerald, silver, topaz, and amethyst.
Finally the man is relieved to hear the monks say, "This is the last key to the last door."
He unlocks the door, turns the knob, and behind that door he is amazed to find the source of that strange sound.
But I can't tell you what it is because you're not a monk.