#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define trav(a, x) for (auto &a : x)
#define pb push_back
#define el "\n";
//#define dbg(x) cerr << "\e[92m" << #x << " = " << x << "\e[97m" << el;
#define dbg(x)
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
ll count_swaps(vector<int> S) {
assert(sz(S) % 2 == 0);
ll n = sz(S) / 2; // number of pairs
vi a = S;
vector<vll> pos(2 * n + 1);
rep(i, 0, 2*n) {
dbg(i);
pos[a[i] + n].pb(i);
dbg(a[i]);
}
ll ans = 0;
ll ind = 0;
while(ind < 2 * n) {
ll cur = a[ind];
auto nxt = upper_bound(all(pos[-cur + n]), ind);
//assert(nxt != pos[-cur + n].end());
//assert(a[*nxt] == -cur);
vi temp;
rep(i, 0, ind) {
temp.pb(a[i]);
}
temp.pb((cur < 0 ? cur : -cur));
temp.pb((cur < 0 ? -cur : cur));
rep(i, ind + 2, 2*n) {
temp.pb(a[i]);
}
ans += (*nxt) - ind - (cur < 0 ? 1 : 0);
//assert(sz(temp) == 2 * n);
ind += 2;
swap(a, temp);
pos.assign(2 * n + 1, vll());
rep(i, 0, 2*n) {
pos[a[i] + n].pb(i);
}
}
return ans;
}
