ABC038_D.cpp

#include <bits/stdc++.h>

using namespace std;

#define int long long
#define all(v) begin(v), end(v)
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define reps(i, s, n) for(int i = (int)(s); i < (int)(n); i++)
#define min(...) min({__VA_ARGS__})
#define max(...) max({__VA_ARGS__})

template<class T1, class T2> void chmin(T1 &a, T2 b){if(a>b)a=b;}
template<class T1, class T2> void chmax(T1 &a, T2 b){if(a<b)a=b;}

using pint = pair<int, int>;
using tint = tuple<int, int, int>;
using vint = vector<int>;

const int inf = 1LL << 55;
const int mod = 1e9 + 7;

// Binary Indexed Tree (1 indexed)
struct BIT
{
  vector<int> data;
  BIT(int n):data(n+1, 0){}
  int query(int k)
  {
    int ret = 0;
    while(k > 0) {
      chmax(ret, data[k]);
      k -= k & -k;
    }
    return ret;
  }
  void update(int k, int x)
  {
    while(k < data.size()) {
      chmax(data[k], x);
      k += k & -k;
    }
  }
};

signed main()
{
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(12);

  int N;
  cin >> N;
  vector< pair<int, int> > box;
  rep(i, N) {
    int w, h;
    cin >> w >> h;
    box.emplace_back(w, -h);
  }
  sort(all(box));
  int dp[100010] = {};
  BIT bit(100010);
  rep(i, N) {
    int h = -box[i].second;
    dp[i] = bit.query(h-1) + 1;
    bit.update(h, dp[i]);
  }
  cout << *max_element(dp, dp + N) << endl;

  return 0;
}