Do not regret the past, just learn from it.”

Ashok, a fresh computer graduate from a world-class University, goes for an
interview in a software company.

The interviewer is Sunder, a grubby old man. And the first question he asks
Ashok is, `Are you good at logic?'

`Of course,' replies Ashok.

`Let me test you,' replies Sunder. `Two men come down a chimney. One comes
with a clean face and the other comes out with a dirty face. Which one would
wash his face?'

Ashok stares at Sunder. `Is that a test in Logic?' Sunder nods.

`The one with the dirty face washes his face', Ashok answers wearily.

`Wrong. The one with the clean face washes his face. Examine the simple
logic. The one with the dirty face looks at the one with the clean face and
thinks his face is clean. The one with the clean face looks at the one with the
dirty face and thinks his face is dirty. So, the one with the clean face washes
his face.'

`Hmm. I never thought of that," says Ashok. `Give me another test.'

Sunder holds up two fingers, `Two men come down a chimney. One comes out with
a clean face and the other comes out with a dirty face. Which one washes his
face?'

`We have already established that. The one with the clean face washes his
face.'

`Wrong. Each one washes one's face. Examine the simple logic. The one with
the dirty face looks at the one with the clean face and thinks his face is
clean. The one with the clean face looks at the one with the dirty face and
thinks his face is dirty. So, the one with the clean face washes his face.
When the one with the dirty face sees the one with the clean face washing his
face, he also washes his face. So each one washes one's face.'

`I didn't think of that!' says Ashok. `It's shocking to me that I could make an
error in logic. Test me again!'

Sunder holds up two fingers, `Two men come down a chimney. One comes out with a
clean face and the other comes out with a dirty face. Which one washes his
face?'

`Each one washes his face.'

`Wrong. Neither one washes his face. Examine the simple logic. The one with
the dirty face looks at the one with the clean face and thinks his face is
clean. The one with the clean face looks at the one with the dirty face and
thinks his face is dirty. But when the one with clean face sees that the one
with the dirty face doesn't wash his face, he also doesn't wash his face. So
neither one washes his face.'

Ashok is desperate. `I am qualified for this job. Please give me one more
test!'

He groans when Sunder lifts his two fingers, `Two men come down a chimney. One
comes out with a clean face and the other comes out with a dirty face. Which
one washes his face?'

`Neither one washes his face', Ashok replies, `I have learnt this logic.'

`Wrong, again. Do you now see, Ashok, why programming knowledge is
insufficient for this job? Tell me, how is it possible for two men to come down
the same chimney, and for one to come out with a clean face and the
other with a dirty face? Don't you see the flaw in the premise?'"