#include<bits/stdc++.h>
#define int long long
#include "shoes.h"
using namespace std;
#define in array<int, 2>
#define pb push_back
#define pob pop_back
#define INF (int)1e17
#define MX (int)3e5+5
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)
struct fenwick
{
vector<int> val;
int N;
void init(int n)
{
N = n+5;
val.assign(N, 0);
return;
}
int sum(int x)
{
int ret = 0;
for(int t = x; t; t-=(t&-t))
ret+=val[t];
return ret;
}
void upd(int x)
{
for(int t = x; t < N; t+=(t&-t))
val[t]++;
return;
}
};
int count_swaps(vector<signed> s)
{
int n = (s.size())/2;
set<int> p[2*n+1];
for(int i = 0; i < 2*n; i++)
p[s[i]+n].insert(i);
vector<in> pr;
int ans = 0;
for(int i = 0; i < 2*n; i++)
{
if(p[s[i]+n].find(i) == p[s[i]+n].end())
continue;//already paired.
if(s[i] > 0)
ans++;
auto fn = p[-s[i]+n].lower_bound(i);
pr.pb({i, *fn});
p[s[i]+n].erase(i);
p[-s[i]+n].erase(fn);
}
sort(pr.begin(), pr.end());
fenwick fen; fen.init(2*n);
for(auto [l, r]: pr)
{
ans+=(r-l-1); ans-=(fen.sum(r+1)-fen.sum(l));
fen.upd(r+1);
}
return ans;
}
