#include <bits/stdc++.h>
using namespace std;
struct seg {
    int start, end;
    seg() { start = end = 0; }
    seg(int s, int e) { start = s, end = e; }
    bool covers(seg& other) { return other.start < start && start < other.end || other.start < end && end < other.end; }
};
int fun(istream& ins) {
    int n;
    ins >> n;
    seg competitions[n];
    vector<seg> added;
    for (int i = 0; i < n; i++) {
        ins >> competitions[i].start >> competitions[i].end;
    }
    for (int i = 0; i < n; i++) {
        bool tmp = true;
        for (int j = 0; j < added.size(); j++)
            if (competitions[i].covers(added[j])) {
                tmp = false;
                break;
            }
        if (tmp) {
            added.push_back(competitions[i]);
        }
    }
    return added.size();
}

#define ensure(func, input, output)  \
    {                                \
        std::stringstream in(input); \
        assert(func(in) == output);  \
    }
//测试
void test() {
    ensure(fun, "3\n0 2\n2 4\n1 3\n", 2);
    ensure(fun, "4\n0 5\n2 3\n4 9\n5 7\n", 2);
    ensure(fun, "3\n0 5\n4 8\n5 10\n", 2);
    ensure(fun, "6\n0 3\n2 6\n3 4\n5 8\n4 5\n2 7\n", 4);
    cout << "All pass!" << endl;
}
int main() {
    // test();
    cout << fun(cin);
    return 0;
}