Mary had a piece of chalk

Mary had a piece of chalk that was as white as cream.
She liked to doodle and to draw whatever she would dream.
One day she came to Harvard Square and got a little bored.
The lazy bums were playing chess, the singers screamed and roared.

She saw a building strange and bright that shimmered in the sun.
"I'll go and check it out", she thought, "that building may be fun".
She walked across the Harvard Yard and faced the Science Center.
She pushed the door, it smoothly turned, allowing her to enter.

Mary explored the ground floor, but nothing much was there,
Except for calculator "Mark" preserved with proper care.
She wondered what was up above, maybe there was more life;
She got into an elevator and pressed the button 5.

The elevator stopped and Mary stepped out into the hall,
Took two left turns, walked through the door and met no one at all.
The offices were open, but no one was in sight,
So Mary sneaked into one room to see what was inside.

A desk covered with papers, a bookshelf wide and tall,
A chair, a computer -- that was about all.
The scribbles on the blackboard were very-very strange,
And there was an ugly picture that was begging for a change.

There was an eraser, but no chalk, said Marry: "What a pity",
Then she took out her own piece and made the picture pretty.
She checked the news from CNN, they were as dull as sin,
And then she wandered out the way she wandered in.

A half an hour later Raoul came back from lunch.
He took a look at the blackboard and had a sudden hunch
Of a clean and neat solution he tried so hard to trace,
Encoded in the picture that stared into his face.

He knew the picture had been changed while he was not around,
But who had pulled that trick on him of course he never found.
He asked his colleagues, asked his friends, but never he could dream
That it was done by Mary-Chris whose chalk was white as cream.

                                                              --Michael Livshits