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

bool comp(int a, int b){
    if(abs(a) == abs(b)){
        return a < b;
    }
    return abs(a) < abs(b);
}

int main(){

    int p,a,e;
    cin >> p >>a;
    vector<int> idop;
    for(int i = 0; i< a; i++){
        int ai,bi;
        cin >> ai >> bi;
        idop.push_back(ai);
        idop.push_back(-1*bi-1);
    }
    cin >> e;
    for(int i = 0; i < e; i++){
        int ai,bi;
        cin >> ai >> bi;
        idop.push_back(ai);
        idop.push_back(-1*bi-1);
    }
    int m=0;
    vector<pair<int, int> > ans;
    sort(idop.begin(), idop.end(),comp);
    pair<int, int> me;
    for(int i = 0; i < idop.size(); i++){

        if(idop[i] > 0) m++;
        if(idop[i] < 0) m--;
        if(m > 0 && me.first == 0){
            me.first = idop[i];

        }
        if(m == 0 && idop[i] < 0){
            me.second = -1*(idop[i]+1);
            ans.push_back(me);
            me.first=0;
            me.second=0;
        }

    }cout << ans.size() << endl;
    for(int i = 0; i< ans.size(); i++){
        cout << ans[i].first << " " << ans[i].second <<endl;
    }
}