#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

typedef pair<int, int> pi;

int main() {
	int n, a, e, ptr = 0;
	cin >> n >> a;
	vector<pi> av(a + 1, { n + 1, n + 1 });
	for (int i = 0; i < a; i++) cin >> av[i].first >> av[i].second;
	cin >> e;
	vector<pi> ans;
	for (int i = 0; i < e; i++) {
		int beg, end;
		cin >> beg >> end;
		while (ptr < a && av[ptr].second < beg) ptr++;
		while (ptr < a && max(av[ptr].first, beg) < min(av[ptr].second, end)) {
			ans.push_back({ max(av[ptr].first, beg), min(av[ptr].second, end) });
			ptr++;
		}
		if (ptr) ptr--;
	}
	cout << ans.size() << "\n";
	for (pi p : ans) cout << p.first << " " << p.second << "\n";
	return 0;
}