Permutation

Rohit collects coins: he has exactly one coin for every year from 1 to n. Naturally, Rohit keeps all the coins in his collection in the order in which they were released. Once Rohit's younger brother made a change — he took all the coins whose release year dated from l to r inclusively and put them in the reverse order. That is, he took a certain segment [l, r] and reversed it. At that, the segmen