*Originally posted by wolfgang59*

**I give two smart guys each a piece of paper with a number on. I tell them that their numbers are consecutive integers and between 1 and N (inclusive). They can only see their own number.
**

Their conversation is as follows;

1st guy: "I dont know your number"

2nd guy: "I dont know your number"

1st guy: "I dont know your number"

2nd guy: "I know your number"

What was N?

1st guy: "I don't know your number"

2nd guy knows 1st guy's number is not 1 or N

2nd guy: "I don't know your number"

1st guy knows 2nd guy's number is not 1 or 2, or N or N-1

1st Guy: "I don't know your number"

2nd Guy know 1st guy's number is not 1 or 2 or 3, or N or N-2 or N-3.

2nd Guy: "I know your number"

2nd guy must have either 3 (so he knows first guys number must be 4), or 4 (so he knows first Guy's number must be 5), or N-3 (so he knows first Guys number must be N-4), or N-4 (so he knows first guys number must be N-5)

We know N must be at least 7, but it can be any number larger than that.

I think we need some other bit of information to get it such as:

"If I now told you the value of N you would know exactly what the 2nd guys number was".