Farmer John, desperate to win the award for best cow photographer at the county fair, is trying to take the perfect photograph of his N cows (2≤N≤2⋅10^5, N even).

Farmer John owns cows of two potential breeds: Guernseys and Holsteins. To make his photo as aesthetic as possible, he wants to line up his cows so that as many Guernseys are in even-numbered positions in the line as possible (the first position in the line is an odd position, the next is an even position, and so on). Due to his lack of strong communication with his cows, the only way he can achieve his goal is by asking even length "prefixes" of his cows to reverse themselves (a prefix consists of the range of cows from the first cow up to the jth cow for some position j).

Please count the minimum number of reversals required for Farmer John to achieve his goal.

#5318 upload 17 done 9 how_to_reg 9

사진촬영 timer 2s memory 256MB

#5318

사진촬영 2s 256MB