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

int main() {
	int p,a;
	cin>>p>>a;
	vector<bool> talalka(p);
	for (int i=0; i<a;i++){
		int x,y;
		cin>>x>>y;
		for (int i=x; i<y;i++){
			talalka[i]=true; 
		}
	}
	int e;
	cin>>e;
	vector<pair<int,int>> ans; 
	for (int i=0; i<e;i++){
		int x,y;
		cin>>x>>y;
		for (int i=x;i<y;i++){
			if (talalka[i]){
				int k=i; 
				while (talalka[i] && i<y){
					i++;
				}
				ans.push_back(make_pair(k,i));
			}
		}
	}
	cout<<ans.size()<<endl;
	for (auto x:ans) cout<<x.first<<" "<<x.second<<endl; 
}