Language: C++

//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,avx512f")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <list>
#include <stack>
#include <queue>
#include <bitset>
#include <numeric>
#include <cassert>
#include <memory>
#include <random>
#include <functional>
#include <complex>
#include <immintrin.h>
#ifdef DEBUG
#include "./Lib/debug_VC.hpp"
#include "./Lib/Timer.hpp"
#include "./Lib/sample.hpp"
#else
#define dump(...)
#endif

/* macro */
#define FOR(i, b, e) for(ll i = (ll)(b); i < (ll)(e); ++i)
#define RFOR(i, b, e) for(ll i = (ll)(e-1); i >= (ll)(b); --i)
#define REP(i, n) FOR(i, 0, n)
#define RREP(i, n) RFOR(i, 0, n)
#define REPC(x,c) for(const auto& x:(c))
#define REPI2(it,b,e) for(auto it = (b); it != (e); ++it)
#define REPI(it,c) REPI2(it, (c).begin(), (c).end())
#define RREPI(it,c) REPI2(it, (c).rbegin(), (c).rend())
#define REPI_ERACE2(it, b, e) for(auto it = (b); it != (e);)
#define REPI_ERACE(it, c) REPI_ERACE2(it, (c).begin(), (c).end())
#define ALL(x) (x).begin(),(x).end()
#define cauto const auto&
/* macro func */
template<class T>
inline auto sort(T& t) { std::sort(ALL(t)); }
template<class T>
inline auto rsort(T& t) { std::sort((t).rbegin(), (t).rend()); }
template<class T>
inline auto unique(T& t) { (t).erase(unique((t).begin(), (t).end()), (t).end()); }
template<class T, class S>
inline auto chmax(T& t, const S& s) { if (s > t) { t = s; return true; } return false; }
template<class T, class S>
inline auto chmin(T& t, const S& s) { if (s < t) { t = s; return true; } return false; }
inline auto BR() { std::cout << "\n"; }

/* type define */
using ll = long long;
using PAIR = std::pair<ll, ll>;
using VS = std::vector<std::string>;
using VL = std::vector<long long>;
using VVL = std::vector<VL>;
using VVVL = std::vector<VVL>;
using VD = std::vector<double>;
template<class T>
using V = std::vector<T>;

/* using std */
using std::cout;
constexpr char endl = '\n';
using std::cin;
using std::pair;
using std::string;
using std::stack;
using std::queue;
using std::vector;
using std::list;
using std::map;
using std::unordered_map;
using std::multimap;
using std::unordered_multimap;
using std::set;
using std::unordered_set;
using std::unordered_multiset;
using std::multiset;
using std::bitset;
using std::priority_queue;

/* Initial processing  */
struct Preprocessing { Preprocessing() { std::cin.tie(0); std::ios::sync_with_stdio(0); }; }_Preprocessing;

/* Remove the source of the bug */
signed pow(signed, signed) { assert(false); return -1; }

/* define hash */
namespace std {
template <>	class hash<std::pair<ll, ll>> { public:	size_t operator()(const std::pair<ll, ll>& x) const { return hash<ll>()(1000000000 * x.first + x.second); } };
}

/* input */
template<class T> std::istream& operator >> (std::istream& is, vector<T>& vec) { for (T& x : vec) is >> x; return is; }

/* constant value */
//constexpr ll MOD = 1000000007;
constexpr ll MOD = 998244353;

//=============================================================================================

auto solve(ll n, const V<PAIR>& v) {

	set<pair<PAIR, PAIR>> s;
	REP(i, n) {
		auto [a, b] = v[i];
		s.emplace(PAIR{a,b}, PAIR{i,1});
		s.emplace(PAIR{b,a}, PAIR{i,2});
	}

	VL state(n); ll cnt = 0;
	ll ans = 0;
	for (auto&& [p, k] : s) {
		state[k.first] += k.second;
		ans += p.first;
		++cnt;
		if (cnt == n) { break; }
	}

	REPC(k, state)if (!(k ^ 3)) {
		return ans;
	}

	V<PAIR> l; l.reserve(n);
	V<PAIR> r; r.reserve(n);
	REP(i, n) {
		((!(state[i] ^ 1)) ? l : r).emplace_back(v[i]);
	}
	if (l.empty() || r.empty()) { return ans; }
	PAIR l1, l2, r1, r2;
	{
		std::sort(ALL(l), [](cauto a, cauto b) {
			if (a.first == b.first) { return a.second > b.second; }
			return a.first > b.first;
		});
		l1 = l[0];
		if (l.size() > 1) {
			l1.second = 1e10;
			FOR(i, 1, l.size()) { chmin(l1.second, l[i].second); }
		}
	}
	{
		std::sort(ALL(l), [](cauto a, cauto b) {
			if (a.second == b.second) { return a.first < b.first; }
			return a.second < b.second;
		});
		l2 = l[0];
		if (l.size() > 1) {
			l2.first = -1;
			FOR(i, 1, l.size()) { chmax(l2.first, l[i].first); }
		}
	}
	{
		std::sort(ALL(r), [](cauto a, cauto b) {
			if (a.first == b.first) { return a.second < b.second;; }
			return a.first < b.first;

		});
		r1 = r[0];
		if (r.size() > 1) {
			r1.second = -1;
			FOR(i, 1, r.size()) { chmax(r1.second, r[i].second); }
		}
	}
	{
		std::sort(ALL(r), [](cauto a, cauto b) {
			if (a.second == b.second) { return a.first > b.first; }
			return a.second > b.second;
		});
		r2 = r[0];
		if (r.size() > 1) {
			r2.first = 1e10;
			FOR(i, 1, r.size()) { chmin(r2.first, r[i].first); }
		}
	}
	ll tmp = ans;
	ans = 1e10;
	auto update = [&ans, &tmp](const PAIR& p1, const PAIR& p2) {
		chmin(ans, tmp - std::max(p1.first, p2.second) + std::min(p1.second, p2.first));
	};
	dump(tmp, l1, l2, r1, r2);
	update(l1, r1);
	update(l2, r1);
	update(l1, r2);
	update(l2, r2);
	return ans;
}

signed main() {
	ll n;
	cin >> n;
	V<PAIR> v;
	v.reserve(n);
	REP(_, n) {
		ll a, b;
		cin >> a >> b;
		v.emplace_back(a, b);
	}
	ll ans = solve(n, v);
	cout << ans << endl;
}

Compiler output:
In file included from /usr/include/c++/14/string:43,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:5:
/usr/include/c++/14/bits/allocator.h: In destructor 'std::_Rb_tree<std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> >, std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> >, std::_Identity<std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> > >, std::less<std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> > >, std::allocator<std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> > > >::_Rb_tree_impl<std::less<std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> > >, true>::~_Rb_tree_impl()':
/usr/include/c++/14/bits/allocator.h:182:7: error: inlining failed in call to 'always_inline' 'std::allocator< <template-parameter-1-1> >::~allocator() noexcept [with _Tp = std::_Rb_tree_node<std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> > >]': target specific option mismatch
  182 |       ~allocator() _GLIBCXX_NOTHROW { }
      |       ^
In file included from /usr/include/c++/14/set:62,
                 from a.cc:11:
/usr/include/c++/14/bits/stl_tree.h:658:16: note: called from here
  658 |         struct _Rb_tree_impl
      |                ^~~~~~~~~~~~~