Project Euler Forum

I am confused by this sentence: "Find the sum of least simultaneous values of all I-expressions pairs made of distinct expressions from file I-expressions.txt (pairs (e1,e2) and (e2,e1) are considered to be identical)."

1) One I-expression ("va") appears twice in that file. Am I meant to count I-expressions paired with "va" once or twice?
2) I think the parenthetical means that I shouldn't count (e1,e2) and (e2,e1) separately. Is that right? (the parenthetical defines what it means for pairs to be "identical" but this is not referenced elsewhere)

My solution didn't look to see if any two lines were the same, so I'd say (1) you're to count the two lines of "va" as two distinct I-expressions and (2) order doesn't matter when pairing up lines, so only look at one of the two possible orderings.

I'm either getting a bad download or I'm not understanding something.
After the 6th expression, there is a line with just 'y'.
My reading of the problem would indicate that valid expressions begin with I( and ends with ). Also all variable values are preceded by ( or , and followed by , or ).
All this would indicate that a stand alone 'y' is invalid.
Further down in the file there are lines 'zb', 'la', 'va' and perhaps more.

It says right there in the very first line of the problem:

We define $\mathcal{I}$-expressions as arithmetic expressions built only from variables names and applications of $\mathcal{I}$.

Ignoring the slight grammar issue, it is clear that lone variables are valid $\mathcal{I}$-expressions. Also beware that some variables have 2 or more characters.

Thank you. Miss read that.