#include <iostream>
#include <vector>

using namespace std;

class int2
{
	public:
	int x;
	int y;
};

int main()
{
	int h, a, e;
	cin >> h;
	vector<int2> Adam;
	
	cin >> a;
	for (int i = 0; i < a; i++)
	{
		int2 in;
		cin >> in.x >> in.y;
		Adam.push_back(in);
	}
	vector<int2> Eva;

	cin >> e;
	for (int i = 0; i < e; i++)
	{
		int2 in;
		cin >> in.x >> in.y;
		Eva.push_back(in);
	}
	int c = 0;
	vector<int2> ans;
	int i = 0, j = 0;

	int x, y;
	while (i < a && j < e)
	{
		x = (Adam[i].x > Eva[j].x ? Adam[i].x : Eva[j].x);
		y = (Adam[i].y < Eva[j].y ? Adam[i].y : Eva[j].y);
		if (x < y)
		{
			c++;
			ans.push_back({ x, y });
		}
		if (Adam[i].y < Eva[j].y)
		{
			i++;
		}
		else
		{
			j++;
		}
	}
	cout << c << endl;
	for (int2 a : ans)
	{
		cout << a.x << " " << a.y << endl;
	}
	cout << endl;
}