#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define dl double
#define st first
#define nd second
#define II pair <int, int>
#include "shoes.h"
using namespace std;
const int N = 5 + 1e5;
const int inf = 7 + 1e9;
struct Fenwick {
int n;
vector <int> tree;
Fenwick (int _n = 0) : n(_n) {
tree.assign(n + 1, 0);
}
void update(int x, int val) {
for (int i = x; i <= n; i += i & -i)
tree[i] += val;
}
int get(int x) {
int ans = 0;
for (int i = x; i > 0; i -= i & -i)
ans += tree[i];
return ans;
}
};
ll count_swaps(vector<int> a) {
int n = (int)a.size() / 2;
vector <queue <int>> q(2 * n + 2);
for (int i = 0; i < 2 * n; i ++)
q[a[i] + n + 1].push(i + 1);
Fenwick f(2 * n + 1);
for (int i = 1; i <= 2 * n + 1; i ++)
f.update(i, 1);
vector <int> vis(2 * n, 1);
int pos = 0;
ll ans = 0;
for (int time = 0; time < n; time ++) {
while (!vis[pos])
pos ++;
int x = a[pos] + n + 1, y = n + 1 - a[pos], u = q[y].front();
q[x].pop(); q[y].pop();
f.update(pos + 1, -1);
ans += f.get(u) - 1 + (a[pos] > 0);
f.update(u, -1);
vis[pos] = 0;
vis[u - 1] = 0;
}
return ans;
}
