DPLIS4

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

#define lb lower_bound
#define vi vector<int>
#define ii pair<int,int>
#define fi first
#define sc second

const int N = 200001;

int n, m;

ii a[N];
set<int> s;
vi bit[N], node[N];

void compress() {
    vector<int> v(s.begin(), s.end());
    for (int i = 1; i <= n; i++) {
        a[i].fi = lower_bound(v.begin(), v.end(), a[i].fi) - v.begin() + 1;
        a[i].sc = lower_bound(v.begin(), v.end(), a[i].sc) - v.begin() + 1;
    }
}

void fakeupd(int i, int j) {
    for (; i <= m; i += i & -i) {
        node[i].push_back(j);
    }
}

void fakeget(int i, int j) {
    for (; i >= 1; i -= i & -i) {
        node[i].push_back(j);
    }
}

void upd(int u, int v, int t) {
    for (int i = u; i <= m; i += i & -i) {
        int j = lb(node[i].begin(), node[i].end(), v) - node[i].begin();
        for (; j < (int) node[i].size(); j += j & -j) {
            bit[i][j] = max(bit[i][j], t);
        }
    }
}

int get(int u, int v) {
    int t = 0;
    for (int i = u; i >= 1; i -= i & -i) {
        int j = lb(node[i].begin(), node[i].end(), v) - node[i].begin();
        for (; j >= 1; j -= j & -j) {
            t = max(t, bit[i][j]);
        }
    }
    return t;
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i].fi >> a[i].sc;
        s.insert(a[i].fi); s.insert(a[i].sc);
    }
    compress(); m = s.size();
    for (int i = 1; i <= m; i++) {
        node[i].push_back(-1);
    }
    for (int i = 1; i <= n; i++) {
        fakeget(a[i].fi, a[i].sc);
        fakeupd(a[i].fi + 1, a[i].sc + 1);
    }
    for (int i = 1; i <= m; i++) {
        sort(node[i].begin(), node[i].end());
        bit[i].resize(node[i].size());
    }
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        int t = get(a[i].fi, a[i].sc) + 1;
        upd(a[i].fi + 1, a[i].sc + 1, t);
        ans = max(ans, t);
    }
    cout << ans << '\n';
}