#include <bits/stdc++.h>
#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define uniq(x) x.erase(unique(all(x)), x.end())
#define rall(x) x.rbegin(), x.rend()
//#define int long long
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;
void setIO() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
}
int64_t count_swaps(vector<int> S) {
int n = sz(S) / 2;
set<int> diff;
for(int &x : S) diff.insert(abs(x));
if(diff.size() == 1) {
ll ans = 0;
int curr = 0;
for(int i=0; i<sz(S); i++) {
if(S[i] < 0) {
ans += 1ll * abs(i - curr);
curr += 2;
}
}
return ans;
}
if(n <= 1000) {
ll ans = 0;
vector<bool> vis(2*n, 0);
for(int i=0; i<2*n; i++) {
if(vis[i]) continue;
vis[i] = true;
int res = 0;
for(int j=i+1; j<2*n; j++) {
if(vis[j]) res--;
if(vis[j]) continue;
if(S[i] + S[j] != 0) continue;
if(S[i] < 0) res += (j - i - 1);
else res += (j - i);
vis[j] = true;
ans += res;
//cout << i+1 << " " << j+1 << ": " << res << '\n';
break;
}
}
return ans;
}
ll ans = 1ll * (n * (n - 1)) / 2;
return ans;
}
// int32_t main() {
// setIO();
// int n;
// cin >> n;
// vector<int> v(2*n);
// for(int &x : v) cin >> x;
// cout << count_swaps(v) << '\n';
// return 0;
// }
