#include <bits/stdc++.h>
using namespace std;
using ll = long long;
// const ll MOD = 1e9+7;

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int p, A; cin >> p >> A;
    vector<pair<int, int>> a(A), b;
    vector<int> elem;
    for (int i = 0; i < A; i++) {
    	cin >> a[i].first >> a[i].second;
    	// elem.push_back(a[i].first); elem.push_back(a[i].second);
    	// elem.push_back(a[i].second+1);
    }
    
    int B; cin >> B;
    b.resize(B);
    for (int i = 0; i < B; i++) {
    	cin >> b[i].first >> b[i].second;
    	// elem.push_back(b[i].first); elem.push_back(b[i].second);
    	// elem.push_back(b[i].second+1);
    }
    
    int l = 0, r = 0;
    vector<array<int, 2>> res;
    while (l < A && r < B) {
    	int s = max(a[l].first, b[r].first);
    	int e = min(a[l].second, b[r].second);
    	if (s < e) res.push_back({s, e});
    	if (s == a[l].first && e == b[r].second) {
    		r++;
    	} else if (s == b[r].first && e == a[l].second) {
    		l++;
    	} else if (s == a[l].first && e == a[l].second) {
    		l++;
    	} else if (s == b[r].first && e == b[r].second) {
    		r++;
    	} else if (a[l].second <= b[l].first) {
    		l++;
    	} else {
    		r++;
    	}
    }
    
    cout << res.size() << "\n";
    for (auto [s, e] : res) cout << s << " " << e << "\n";

    return 0;
}