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

int main() {
	int p;
	cin >> p;
	int n;
	cin >> n;
	vector<pair<int, int>> v;
	for (int i = 0; i < n; ++i) {
		int a, b;
		cin >> a >> b;
		v.push_back({a, b});
	}
	int m;
	cin >> m;
	for (int i = 0; i < m; ++i) {
		int a, b;
		cin >> a >> b;
		v.push_back({a, b});
	}
	sort(v.begin(), v.end());
	vector<pair<int, int>> ans;

	for (int i = 0; i < n + m; ++i) {
		if (!ans.empty() && v[i].first <= ans.back().second) {
			ans.back().second = max(ans.back().second, v[i].second);
		} else {
			ans.push_back(v[i]);
		}
	}

	cout << ans.size() << endl;
	for (auto [a, b] : ans) {
		cout << a << " " << b << endl;
	}
}