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

// ??LIS?????
int LIS(vector<int>& A) {
    vector<int> dp;
    for (int x : A) {
        auto it = lower_bound(dp.begin(), dp.end(), x);
        if (it == dp.end()) dp.push_back(x);
        else *it = x;
    }
    return dp.size();
}

// ??????????
int optimizedSimulatedAnnealing(int n, vector<pair<int, int>>& range) {
    // ???????????????
    vector<int> A(n);
    for (int i = 0; i < n; i++) {
        A[i] = rand() % (range[i].second - range[i].first + 1) + range[i].first;
    }

    // ????LIS??
    int bestLIS = LIS(A);
    vector<int> bestA = A;

    // ???????
    double temperature = 100.0;
    double coolingRate = 0.995;

    // ??????
    while (temperature > 1e-6) {
        // ????????????????
        vector<int> newA = A;
        int numChanges = rand() % (n / 10);  // ???????

        // ????????
        for (int i = 0; i < numChanges; i++) {
            int idx = rand() % n;
            newA[idx] = rand() % (range[idx].second - range[idx].first + 1) + range[idx].first;
        }

        // ????LIS??
        int newLIS = LIS(newA);

        // ???????????
        if (newLIS > bestLIS) {
            bestLIS = newLIS;
            bestA = newA;
        } else {
            // ?????????????????????
            double prob = exp((newLIS - bestLIS) / temperature);
            if (rand() / double(RAND_MAX) < prob) {
                bestLIS = newLIS;
                bestA = newA;
            }
        }

        // ??
        temperature *= coolingRate;
    }

    return bestLIS;
}

int main() {
    int n;
    cin >> n;

    // ????
    vector<pair<int, int>> range(n);
    for (int i = 0; i < n; i++) {
        cin >> range[i].first >> range[i].second;
    }

    // ??????????????
    int maxLIS = optimizedSimulatedAnnealing(n, range);

    cout << maxLIS << endl;
    return 0;
}