/**
 * @author n685
 * @brief
 * @date 2024-10-02 17:47:12
 *
 *
 */
#include <utility>

#include "bits/stdc++.h"

#ifdef LOCAL
#include "dd/debug.h"
#else
#define dbg(...) 42
#define dbg_proj(...) 420
#define dbg_rproj(...) 420420
void nline() {}
void bar() {}
void start_clock() {}
void end_clock() {}
#endif

namespace rs = std::ranges;
namespace rv = std::views;

struct Node {
  std::array<int, 2> ch{-1, -1};
};
struct Seg {
  int sz{};
  std::vector<Node> data;
  std::vector<int> rts;
  Seg() = default;
  explicit Seg(int sz_, int nrts)
      : sz{static_cast<int>(std::bit_ceil<uint32_t>(sz_))},
        rts(nrts, -1) {}
  int copy_node(int ind) {
    if (ind == -1) {
      data.emplace_back();
    } else {
      data.push_back(data[ind]);
    }
    return static_cast<int>(data.size()) - 1;
  }
  void nch(int node, int ch) {
    int ind = copy_node(data[node].ch[ch]);
    data[node].ch[ch] = ind;
  }
  void upd(int i, int node, int l, int r) {
    if (l == r) {
      return;
    }
    int mid = (l + r) / 2;
    if (i <= mid) {
      nch(node, 0);
      upd(i, data[node].ch[0], l, mid);
    } else {
      nch(node, 1);
      upd(i, data[node].ch[1], mid + 1, r);
    }
  }
  void upd(int t, int i) { upd(i, rts[t], 0, sz - 1); }
  bool is_there(int i, int node, int l, int r) {
    if (l == r) {
      return true;
    }
    int mid = (l + r) / 2;
    if (i <= mid) {
      if (data[node].ch[0] == -1) {
        return false;
      }
      return is_there(i, data[node].ch[0], l, mid);
    }
    if (data[node].ch[1] == -1) {
      return false;
    }
    return is_there(i, data[node].ch[1], mid + 1, r);
  }
  bool is_there(int t, int i) { return is_there(i, rts[t], 0, sz - 1); }
  void new_rt(int ind) { rts[ind] = copy_node(-1); }
  void copy_rt(int rc, int ind) { rts[rc] = copy_node(rts[ind]); }
#ifdef LOCAL
  void debug(std::vector<int> &s, int ll, int rr, int node, int l, int r) {
    if (l == r) {
      s.push_back(l);
    }
    int mid = (l + r) / 2;
    if (data[node].ch[0] != -1 && ll <= mid) {
      debug(s, ll, rr, data[node].ch[0], l, mid);
    }
    if (data[node].ch[1] != -1 && rr > mid) {
      debug(s, ll, rr, data[node].ch[1], mid + 1, r);
    }
  }
  std::vector<int> debug(int t, int ll, int rr) {
    std::vector<int> ans;
    debug(ans, ll, rr, rts[t], 0, sz - 1);
    return ans;
  }
#else
  std::string debug(int t) { return ""; }
#endif
};

struct II {
  int l, r;
};

struct Flow {
  int sz, s = -1, t = -1;
  std::vector<int> vis;
  Seg &adj;
  std::vector<II> &ii;
  std::vector<int> left;
  std::vector<bool> is_left;
  explicit Flow(
    int _sz,
    Seg &adj_,
    std::vector<II> &ii_,
    std::vector<int> left_
  )
      : sz(_sz),
        vis(sz, -1),
        adj(adj_),
        ii(ii_),
        left(std::move(left_)),
        is_left(sz) {
    for (int i : left) {
      is_left[i] = true;
    }
  }

  std::vector<int> l, h;
  void bfs() {
    l.assign(sz, static_cast<int>(1e9));
    l[s] = 0;
    std::queue<int> q;
    q.push(s);
    while (!q.empty()) {
      int node = q.front();
      q.pop();
      if (node == s) {
        for (int i : left) {
          if (vis[i] == -1 && l[i] > l[node] + 1) {
            l[i] = l[node] + 1;
            q.push(i);
          }
        }
      } else if (is_left[node]) {
        for (int i = ii[node].l; i < ii[node].r; ++i) {
          if (vis[node] != i && adj.is_there(node, i) && l[i] > l[node] + 1) {
            l[i] = l[node] + 1;
            q.push(i);
          }
        }
      } else if (node != t) {
        if (vis[node] == -1 && l[t] > l[node] + 1) {
          l[t] = l[node] + 1;
        } else {
          for (int i = ii[node].l; i < ii[node].r; ++i) {
            if (vis[i] == node && adj.is_there(node, i) && l[i] > l[node] + 1) {
              l[i] = l[node] + 1;
              q.push(i);
            }
          }
        }
      }
      // for (Edge &e : adj[node]) {
      //   if (e.cap > 0 && l[e.v] > l[node] + 1) {
      //     l[e.v] = l[node] + 1;
      //     q.push(e.v);
      //   }
      // }
    }
  }
  int dfs(int node) {
    if (node == t) {
      return 1;
    }
    if (node == s) {
      for (; h[node] < static_cast<int>(left.size()); ++h[node]) {
        int i = left[h[node]];
        if (vis[i] == -1 && l[i] == l[node] + 1) {
          int val = dfs(i);
          if (val != -1) {
            vis[i] = val;
            return 1;
          }
        }
      }
    } else if (is_left[node]) {
      if (h[node] == 0) {
        h[node] = ii[node].l;
      }
      for (; h[node] < ii[node].r; ++h[node]) {
        int i = h[node];
        if (vis[node] != i && adj.is_there(node, i) && l[i] == l[node] + 1) {
          int val = dfs(i);
          if (val != -1) {
            vis[i] = node;
            vis[node] = i;
            return i;
          }
        }
      }
    } else {
      if (vis[node] == -1 && l[t] == l[node] + 1) {
        return 1;
      }
      if (h[node] == 0) {
        h[node] = ii[node].l;
      }
      for (; h[node] < ii[node].r; ++h[node]) {
        int i = h[node];
        if (vis[i] == node && adj.is_there(node, i) && l[i] == l[node] + 1) {
          int val = dfs(i);
          if (val != -1) {
            return 1;
          }
        }
      }
    }
    // for (; h[node] < static_cast<int>(adj[node].size()); ++h[node]) {
    //   Edge &e = adj[node][h[node]];
    //   if (e.cap > 0 && l[e.v] == l[node] + 1) {
    //     T val = dfs(e.v, std::min(f, e.cap));
    //     if (val) {
    //       e.cap -= val;
    //       adj[e.v][e.rev].cap += val;
    //       return val;
    //     }
    //   }
    // }
    return -1;
  }
  int max_flow(int _s, int _t) {
    s = _s;
    t = _t;
    bfs();
    int ans = 0;
    while (l[t] != static_cast<int>(1e9)) {
      h.assign(sz, 0);
      // ans += dfs(s, std::numeric_limits<T>::max());
      int res;
      do {
        res = dfs(s);
        if (res == -1) {
          break;
        }
        ans += res;
      } while (res != -1);
      bfs();
    }
    return ans;
  }
};

int main() {
#ifndef LOCAL
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
#endif
  start_clock();

  int n;
  std::cin >> n;

  std::vector<II> ii(n);
  std::vector<II> both(2 * n);
  std::vector<int> left;
  for (auto &[l, r] : ii) {
    std::cin >> l >> r;
    --l;
    --r;
    left.push_back(l);
  }
  rs::sort(ii, {}, &II::l);
  for (int i = 0; i < n; ++i) {
    both[ii[i].l] = ii[i];
    both[ii[i].r] = ii[i];
  }

  Seg adj(2 * n, 2 * n);
  for (int i = 0; i < n; ++i) {
    if (i == 0) {
      adj.new_rt(ii[i].l);
    } else {
      adj.copy_rt(ii[i].l, ii[i - 1].l);
    }
    if (i > 0) {
      adj.upd(ii[i].l, ii[i - 1].r);
    }
  }
  rs::sort(ii, {}, &II::r);
  for (int i = n - 1; i >= 0; --i) {
    if (i == n - 1) {
      adj.new_rt(ii[i].r);
    } else {
      adj.copy_rt(ii[i].r, ii[i + 1].r);
    }
    if (i < n - 1) {
      adj.upd(ii[i].r, ii[i + 1].l);
    }
  }
#ifdef LOCAL
  for (auto &[l, r] : ii) {
    dbg(l, adj.debug(l, l, r - 1));
  }
#endif
  const int s = 2 * n, t = 2 * n + 1;
  Flow flow(2 * n + 2, adj, both, left);
  std::cout << 2 * n - flow.max_flow(s, t) << '\n';
  end_clock();
}