Submission #1593385

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Source Code Expand

from collections import defaultdict, Counter
from itertools import product, groupby, count, permutations, combinations
from math import pi, sqrt
from collections import deque
from bisect import bisect, bisect_left, bisect_right
INF = 10 ** 10


def ceil(a, b):
    return (a + b - 1) // b


def main():
    N = int(input())
    A_list = list(sorted([(int(input()), i) for i in range(N)]))
    a_list = [i for a, i in A_list]
    ans = 0
    for i, a in enumerate(a_list):
        ans += (i % 2 != a % 2)
    print(ceil(ans, 2))


if __name__ == '__main__':
    main()

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