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


int main() {
    int n;
    cin >> n;

    int a;
    cin >> a;
    queue<pair<int, int>> adam;
    for(int i = 0;i < a;i++ ) {
        int x, y;
        cin >> x >> y;
        adam.push({x, y});
    }
    int b;
    cin >> b;
    vector<pair<int, int>> eva;
    for(int i = 0;i < b;i++ ) {
        int x, y;
        cin >> x >> y;
        eva.push_back({x, y});
    }
    int i = 0;

    vector<pair<int, int>> ans;

    while(!adam.empty()) {
        auto x = adam.front();

        for(int i = 0;i < b;i++) {
            if(x.second <= eva[i].first) {
                adam.pop();
                break;
            } else if(eva[i].second >= x.second && eva[i].first <= x.first) {
                ans.push_back({x.first, x.second});
            } else if(eva[i].second >= x.second && eva[i].first >= x.first) {
                ans.push_back({eva[i].first, x.second});
            } else if(eva[i].second <= x.second && x.first <= eva[i].second) {
                ans.push_back({x.first, eva[i].second});
            }
        }

        if(i == b) break;
    }
    

    cout << ans.size() << '\n';
    for(auto x : ans) {
        cout << x.first << ' ' << x.second << '\n';
    }
    return 0;
}