#include <iostream>
#include <set>
#include <map>
using namespace std;

int main() {
	
	int n;
	set<pair<int, int> > s1, s2;
	map<pair<int, int>, int> mp1, mp2;
	cin >> n;
	int c1 = 0, c2 = 0;
	for(int i = 0, a, b; i < n;++i){
		cin >> a >> b;
		s1.insert({a, b});
		s2.insert({b, a});
		++mp1[{a, b}];
		++mp2[{b, a}];
	}
	long long sum = 0;
	while(c1 < n / 2 && c2 < n / 2){
		auto a = s1.rbegin(), b = s2.rbegin();
		if(a->first + b->second > b->first + a->second && (a->first != b->second || b->first != a->second)){
			--mp2[{a->second, a->first}];
			--mp1[*a];
			sum += a->first;
			if(mp1[*a] == 0){
				s2.erase({a->second, a->first});
				s1.erase(*a);
			}
			++c1;
		}
		else if(a->first != b->second || b->first != a->second){
			--mp2[*b];
			--mp1[{b->second, b->first}];
			sum += b->first;
			if(mp2[*b] == 0){
				s1.erase({b->second, b->first});
				s2.erase(*b);
			}
			++c2;
		}
		else{
			if(mp1[*a] > 1){
				mp1[*a] -= 2;
				mp2[{a->second, a->first}] -= 2;
				
				sum += a->first;
				if(mp1[*a] == 0){
					s2.erase({a->second, a->first});
					s1.erase(*a);
				}
				++c1;
			}
			else{
				--mp2[*b];
				--mp1[{b->second, b->first}];
				pair<int,int>p = *a;
				if(mp2[*b] == 0){
					s1.erase({b->second, b->first});
					s2.erase(*b);
				}
				a = s1.rbegin(), b = s2.rbegin();
				if(a->first + p.second> b->first + p.first){
					++c2;
					sum+= p.second;
				}
				else{
					sum+=p.first;
					++c1;
				}
			}
		}
	}
	while(c1 < n / 2){
		auto a = s1.begin();
		--mp1[*a];
		--mp2[{a->second, a->first}];
		sum += a->first;
		if(mp1[*a] == 0){
			s2.erase({a->second, a->first});
			s1.erase(*a);
		}
		++c1;
	}
	
	while(c2 < n / 2){
		
		auto b = s2.begin();
		--mp2[*b];
		--mp1[{b->second, b->first}];
		sum += b->first;
		if(mp2[*b] == 0){
			s1.erase({b->second, b->first});
			s2.erase(*b);
		}
		++c2;
	}
	cout << sum;
	return 0;
}