#include "shoes.h"
#include <cstdio>
#include <cassert>
using namespace std;
//#include "shoes.h"
#include <bits/stdc++.h>
#define MAXN 200010
#define DELTA 100001
#define pb push_back
#define ll long long
#define fi first
#define se second
#define mp make_pair
//using namespace std;
int n, t[4*MAXN], par[MAXN], tleaf[MAXN];
queue<int> posOf[MAXN];
void build(int v, int tl, int tr)
{
if (tl == tr)
t[v] = 1;
else
{
int tm = (tl + tr) / 2;
build(v*2, tl, tm);
build(v*2+1, tm+1, tr);
t[v] = t[v*2] + t[v*2+1];
}
}
int sum(int v, int tl, int tr, int l, int r)
{
if (l > r)
return 0;
if (l == tl && r == tr)
return t[v];
int tm = (tl + tr) / 2;
return sum(v*2, tl, tm, l, min(r, tm)) + sum(v*2+1, tm+1, tr, max(l, tm+1), r);
}
void update(int v, int tl, int tr, int pos)
{
if (tl == tr)
t[v] = 0;
else
{
int tm = (tl + tr) / 2;
if (pos <= tm)
update(v*2, tl, tm, pos);
else
update(v*2+1, tm+1, tr, pos);
t[v] = t[v*2] + t[v*2+1];
}
}
long long count_swaps(std::vector<int> s)
{
n = s.size();
for (int i = 0; i < n; i++)
{
tleaf[i] = 1;
int other = DELTA - s[i];
if (!posOf[other].empty())
{
par[i] = posOf[other].front();
posOf[other].pop();
}
else
{
par[i] = -1;
posOf[s[i]+DELTA].push(i);
}
}
build(1, 0, n-1);
int res = 0;
for (int i = n-1; i >= 0; i--)
{
if (tleaf[i] == 1)
{
res += sum(1, 0, n-1, par[i]+1, i-1);
tleaf[par[i]] = 0;
update(1, 0, n-1, par[i]);
if (s[i] < 0) res++;
}
}
return res;
}
int main() {
int n;
assert(1 == scanf("%d", &n));
vector<int> S(2 * n);
for (int i = 0; i < 2 * n; i++)
assert(1 == scanf("%d", &S[i]));
fclose(stdin);
long long result = count_swaps(S);
printf("%lld\n", result);
fclose(stdout);
return 0;
}
/*
2
2 1 -1 -2
3
-2 2 2 -2 -2 2
*/
Compilation message
/usr/bin/ld: /tmp/ccufpq7m.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccxJhlCk.o:shoes.cpp:(.text.startup+0x0): first defined here
collect2: error: ld returned 1 exit status
