#include <bits/stdc++.h> 
#define F first 
#define S second 
#define MAX 10000003 
using namespace std; 
#define ll long long int
#include<fstream>
#define MOD 1000000007
#define fast ios_base::sync_with_stdio(false);
#define io   cin.tie(NULL);
#define inp(arr,n) for(ll i=0;i<n;i++){cin>>arr[i];}
#define print(arr,n) for(ll i=0;i<n;i++){cout<<arr[i]<<" ";}
ll power(ll a, ll b) { //a^b
  ll res = 1;
  a = a % MOD;
  while (b > 0) {
    if (b & 1) {res = (res * a) % MOD; b--;}
    a = (a * a) % MOD;
    b >>= 1;
  }
  return res;
}
  ll multiply(ll a, ll b, ll mod) 
{ 
   return ((a % mod) * (b % mod)) % mod; 
} 
ll func(ll arr[],ll siz)
{
  ll sum=0;
  ll ma=0;
  for(ll i=0;i<siz;i++)
  {
    sum+=arr[i];
    ma=max(sum,ma);
  }
  return ma;
}
long long gcd(long long int a, long long int b)
{
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
 
// Function to return LCM of two numbers 
long long lcm(int a, int b)
{
    return (a / gcd(a, b)) * b;
}
std::vector<ll> adj[400005];
std::vector<ll> vis(400005,0);
ll coun;
int f;
void dfs(ll x,ll parent)
{ 
  vis[x]=1;
  coun+=1;
  for(ll k=0;k<adj[x].size();k++)
  {
    if(vis[adj[x][k]]==0)
      dfs(adj[x][k],x);
    else
      {
        if(adj[x][k]!=parent)
          f=1;
      }
  }
}
int main()
{
  ll t;
  t=1;
  while(t--)
  {
    ll n;cin>>n;set<ll> s;
    for(ll i=0;i<n;i++)
    {
      ll a,b;
      cin>>a>>b;
      s.insert(a);
      s.insert(b);
      adj[a].push_back(b);
      adj[b].push_back(a);
    }
    ll ans=0;
    for(auto it=s.begin();it!=s.end();it++)
    {
      if(vis[*it]==0)
      {
        coun=0;
        f=0;
        dfs(*it,-1);
        if(f==0)
          ans+=coun-1;
        else
          ans+=coun;
      }
    }
    cout<<ans<<endl;
  }
  return 0;
}
//DUEL
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define x first
#define y second
#define pii pair<int,int>
#define pb push_back
#define eb emplace_back
#pragma GCC optimize("unroll-loops")
#define shandom_ruffle(a, b) shuffle(a, b, rng)
#define vi vector<int>
#define vl vector<ll>
#define popcnt __builtin_popcount
#define popcntll __builtin_popcountll
#define all(a) begin(a),end(a)

using namespace std;
using namespace __gnu_pbds;

using ll=long long;
using ull=unsigned long long;
using ld=long double;
int MOD=1000000007;
int MOD2=998244353;
vector<int> bases;
const ll LLINF=1ll<<60;
const char en='\n';

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void yes() {cout<<"YES"<<en; exit(0);}
void no() {cout<<"NO"<<en; exit(0);}
inline int rund() {int x576363482791fuweh=rng();return abs(x576363482791fuweh)%RAND_MAX;}
template<class T>
void prVec(vector<T> w,bool fl=false)
{
	cout<<w.size()<<en;
	for (int i=0;i<int(w.size())-1;++i) cout<<w[i]<<' ';
	if (w.size()) cout<<w[w.size()-1]<<en;
	if (fl) cout<<flush;
}

void M998()
{
	swap(MOD,MOD2);
}

ll raand()
{
	ll a=rund();
	a*=RAND_MAX;
	a+=rund();
    return a;
}

#define rand raand

ll raaand()
{
	return raand()*(MOD-7)+raand();
}

template<class T>
vi compress(vector<T>&v)
{
	set<T> s;
	for (auto a: v) s.insert(a);
	vector<T> o(all(s));
	vi nv;
	for (int i=0;i<(int)v.size();++i) nv.pb(lower_bound(all(o),v[i])-o.begin());
	return nv;
}

string to_upper(string a)
{
	for (int i=0;i<(int)a.size();++i) if (a[i]>='a' && a[i]<='z') a[i]-='a'-'A';
	return a;
}

string to_lower(string a)
{
	for (int i=0;i<(int)a.size();++i) if (a[i]>='A' && a[i]<='Z') a[i]+='a'-'A';
	return a;
}

ll sti(string a,int base=10)
{
	ll k=0;
	for (int i=0;i<(int)a.size();++i)
	{
		k*=base;
		k+=a[i]-'0';
	}
	return k;
}

template<class T>
void eras(vector<T>& a,T b)
{
	a.erase(find(a.begin(),a.end(),b));
}

string its(ll k,int base=10)
{
	if (k==0) return "0";
	string a;
	while (k)
	{
		a.push_back((k%base)+'0');
		k/=base;
	}
	reverse(a.begin(),a.end());
	return a;
}

ll min(ll a,int b)
{
	if (a<b) return a;
	return b;
}

ll min(int a,ll b)
{
	if (a<b) return a;
	return b;
}

ll max(ll a,int b)
{
	if (a>b) return a;
	return b;
}

ll max(int a,ll b)
{
	if (a>b) return a;
	return b;
}

ll gcd(ll a,ll b)
{
	if (b==0) return a;
	return gcd(b,a%b);
}

ll lcm(ll a,ll b)
{
	return a/gcd(a,b)*b;
}

template<class T,class K>
pair<T,K> mp(T a,K b)
{
	return make_pair(a,b);
}

inline int mult(ll a,ll b)
{
	return (a*b)%MOD;
}

inline int pot(int n,int k)
{
	if (k==0) return 1;
	ll a=pot(n,k/2);
	a=mult(a,a);
	if (k%2) return mult(a,n);
	else return a;
}

int divide(int a,int b)
{
	return mult(a,pot(b,MOD-2));
}

inline int sub(int a,int b)
{
	if (a-b>=0) return a-b;
	return a-b+MOD;
}

inline int add(int a,int b)
{
	if (a+b>=MOD) return a+b-MOD;
	return a+b;
}

void ad(int&a,int b)
{
	a+=b;
	if (a>=MOD) a-=MOD;
}

bool prime(ll a)
{
	if (a==1) return 0;
	for (int i=2;i<=round(sqrt(a));++i)
	{
		if (a%i==0) return 0;
	}
	return 1;
}

int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};
const int N=400010,M=1<<18;
int t,n,h[N];

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	for (int i=0;i<10;++i) bases.push_back(rand()%(MOD-13893829*2)+13893829);
	cin>>n;
	multiset<int> s;
	ll an=0;
	for (int i=0;i<2*n;++i) cin>>h[i],an+=h[i];
	for (int i=1;i<=n;++i)
	{
		s.insert(h[n-i]);
		s.insert(h[n+i-1]);
		an-=*s.begin();
		s.erase(s.begin());
	}
	cout<<an<<en;
}





