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

int main(){
    int p, a; cin >> p >> a;
    vector<bool> idopontok(p);
    for (int i=0;i<a;i++){
        int AK, AV;
        cin >> AK >> AV;
        for (int j=AK;j<AV;j++){
            idopontok[j]=true;
        }
    }
    int e; cin >> e;
    vector<pair<int,int>> v;
	for (int i=0;i<e;i++){
		int EK,EV;
		cin >> EK >> EV;
		for (int j=EK;j<EV;j++){
			if (idopontok[j]){
				int k=j;
				while (idopontok[j] and j<EV){
					j++;
				}
				v.push_back(make_pair(k,j));
			}
		}
	}
	cout << v.size() << "\n";
	for (auto ki:v){
            cout << ki.first <<" "<< ki.second << "\n";
	}
}