#include <iostream>
#include <vector> 

using namespace std;
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int p;
	cin >> p;
	vector<int> a;
	vector<int> b;
	vector<int> megoldas;
	int adam, eva;
	cin >> adam;
	for (int i = 0; i < adam; ++i)
	{
		int x, y;
		cin >> x >> y;
		a.push_back(x);
		a.push_back(y);
	}
	cin >> eva;
	for (int i = 0; i < eva; ++i)
	{
		int x, y;
		cin >> x >> y;
		b.push_back(x);
		b.push_back(y);
	}
	int ad=0, ev=0;
	while (ad < a.size() and ev < b.size())
	{
		int start = max(a[ad], b[ev]);
		int vege = min(a[ad + 1], b[ev + 1]);
		if (start < vege)
		{
			megoldas.push_back(start);
			megoldas.push_back(vege);
		}
		if (a[ad + 1] < b[ev + 1]) ad += 2;
		else ev += 2;
	}
	cout << megoldas.size() / 2 << endl;
	for (int index = 0; index < megoldas.size(); index+=2) cout << megoldas[index] << " "<<megoldas[index + 1] << " "<<endl;
	return 0;
}