#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
struct lesson {
    double start;
    double finish;
    bool operator < (lesson& rhs) {
        return finish < rhs.finish;
    }
};

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

    if (n == 0) {
        cout << 0;
        return 0;
    }

    vector <lesson> v(n);
    for (auto& elem : v) {
        cin >> elem.start;
        cin >> elem.finish;
    }

    sort(v.begin(), v.end());

    vector <int> result;
    result.push_back(0);

    for (int i = 1; i < v.size(); ++i) {
        if (v[result.back()].finish > v[i].start) {
            continue;
        }
        result.push_back(i);
    }

    cout << result.size() << endl;
    for (int i = 0; i < result.size(); ++i) {
        cout << v[result[i]].start << " " << v[result[i]].finish << endl;
    }

    return 0;
}