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

int main() {
	int p,a;
	cin>>p>>a;
	vector<int> ad;
	ad.assign(p+1, 0);
	int mx=0;
	for (int i=0; i<a;i++){
		int x,y;
		cin>>x>>y; 
		ad[x]=1; 
		ad[y]=-1;
		mx=max(mx, y);
	} 
	int e;
	cin>>e;
	vector<int> ev;
	ev.assign(p+1, 0);
	for (int i=0; i<e;i++){
		int x,y;
		cin>>x>>y;
		
		ev[x]=1;
		ev[y]=-1;
		mx=max(mx,y);
	}
	vector<pair<int,int>> ans; 
	bool adi=false, evi=false;  
	for (int i=0; i<mx;i++){
		if (ad[i]==1) adi=true;
		if (ad[i]==-1) adi=false;
		if (ev[i]==1) evi=true;
		if (ev[i]==-1) evi=false;
		
		if(adi && evi){
			int k=i,v;
			while (ev[i]!=-1 && ad[i]!=-1){
				i++;
			}
			v=i;
			i--;
			ans.push_back({k,v});
		}
	}
	cout<<ans.size()<<endl;
	for (auto ins:ans) cout<<ins.first<<" "<<ins.second<<endl;
}