牛客网多校联赛第五场D

#include<bits/stdc++.h>
using  namespace std;

typedef long long ll;
const int MAX_N = 2e5 + 5;
int bit[MAX_N], a[MAX_N];
int n;

void add(int i) {
	for (; i <= n; i += i&(-i)) {
		bit[i]++;
	}
}
ll sum(int i) {
	ll res = 0;
	for (; i; i -= i & (-i))
		res += bit[i];
	return res;
}

int main() {
	ll res = 0;
	scanf("%d", &n);
	for (int i = 0; i < n / 2; i++) scanf("%d", &a[i]), a[i] /= 2;
	for (int i = 0; i < n / 2; i++) {
		res += i - sum(a[i]);
		add(a[i]);
	}
	priority_queue<int> que;
	for (int i = 0; i < n / 2; i++) {
		que.push(a[i]);
		if (que.top() > a[i]) {
			res += que.top() - a[i];
			que.pop();
			que.push(a[i]);
		}
	}
	cout << res << endl;
}