1. The problem statement, all variables and given/known data Find the sign of the permutation --> Picture here: http://tinypic.com/view.php?pic=2q8rkso&s=5 No other given data. 2. Relevant equations ε(σ) = (-1)^m(σ). If i < j and σ(i) > σ(j) then there's an inversion. Where ε(σ) denotes the sign of the permutation and m(σ) the number of inversions. 3. The attempt at a solution What I tried to do is this: σ(1) = 2n + 1 σ(2) = 2n 2n + 1 > 2n -- yes Now what? Should I go on doing the same? I mean, if the permutation belongs directly to S2, S3 or any other number you can count the inversions but how do I count the inversions now? Thank you.