#include<bits/stdc++.h>
using namespace std;

const int INF = 1 << 28;

struct Primal_Dual
{
  typedef pair< int, int > Pi;
 
  struct edge
  {
    int to, cap, cost, rev;
  };
  vector< vector< edge > > graph;
  vector< int > potential, min_cost, prevv, preve;
 
  Primal_Dual(int V):graph(V){}
 
  void add_edge(int from, int to, int cap, int cost)
  {
    graph[from].push_back((edge){to, cap, cost, (int)graph[to].size()});
    graph[to].push_back((edge){from, 0, -cost, (int)graph[from].size() - 1});
  }
 
  int min_cost_flow(int s,int t,int f)
  {
    
    int V = graph.size(), ret = 0;
    priority_queue< Pi, vector< Pi >, greater< Pi > > que;
    potential.assign(V, 0);
    prevv.assign(V, -1);
    preve.assign(V, -1);

    while(f > 0){
      min_cost.assign(V, INF);

      que.push(Pi(0, s));
      min_cost[s] = 0;
      while(!que.empty()){
        Pi p = que.top(); que.pop();
        if(min_cost[p.second] < p.first) continue;
        for(int i = 0; i < graph[p.second].size(); i++){
          edge& e = graph[p.second][i];
          int nextCost = min_cost[p.second] + e.cost + potential[p.second] - potential[e.to];
          if(e.cap > 0 && min_cost[e.to] > nextCost){
            min_cost[e.to] = nextCost;
            prevv[e.to] = p.second, preve[e.to] = i;
            que.push(Pi(min_cost[e.to], e.to));

          }
        }
      }

      if(min_cost[t] == INF) return(ret);
      for(int v = 0; v < V; v++) potential[v] += min_cost[v];
      int addflow = f;
      for(int v = t; v != s; v = prevv[v]){
        addflow = min( addflow, graph[prevv[v]][preve[v]].cap);
      }
      f -= addflow;
      ret += addflow * potential[t];
      for(int v = t; v != s; v = prevv[v]){
        edge& e = graph[prevv[v]][preve[v]];
        e.cap -= addflow;
        graph[v][e.rev].cap += addflow;
      }
    }
    return(ret);
  }
};

int main()
{
  int N, A[1000], B[1000];
  cin >> N;
  vector< int > nums;
  for(int i = 0; i < N; i++) {
    cin >> A[i] >> B[i];
    nums.push_back(A[i]);
    nums.push_back(B[i]);
  }
  sort(nums.begin(), nums.end());
  nums.erase(unique(nums.begin(), nums.end()), nums.end());
 
  int s = N + nums.size() + 1, g = s + 1;

  Primal_Dual MCF(g + 1);
  int ret = 0;
  for(int i = 0; i < N; i++) {
    A[i] = lower_bound(nums.begin(), nums.end(), A[i]) - nums.begin();
    B[i] = lower_bound(nums.begin(), nums.end(), B[i]) - nums.begin();
    MCF.add_edge(s, i, 1, 0);
    MCF.add_edge(i, N + A[i], 1, nums[A[i]]);
    MCF.add_edge(i, N + B[i], 1, nums[B[i]]);
    MCF.add_edge(i, N + nums.size(), 1, nums[A[i]] + nums[B[i]]);
    ret += nums[A[i]] + nums[B[i]];
  }

  for(int i = 0; i < nums.size(); i++) {
    MCF.add_edge(N + i, g, 1, 0);
  }

  MCF.add_edge(N + nums.size(), g, INF, 0);
  for(int i = 0; i < N; ++i) {
    ret -= MCF.min_cost_flow(s, g, 1);
  }
  cout << ret << endl;
}