#include <bits/stdc++.h>
#include <random>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> p32;
typedef pair<ll, ll> p64;
typedef pair<double, double> pdd;
typedef vector<ll> v64;
typedef vector<int> v32;
typedef vector<vector<int>> vv32;
typedef vector<vector<ll>> vv64;
typedef vector<vector<p64>> vvp64;
typedef vector<p64> vp64;
typedef vector<p32> vp32;
ll MOD = 998244353;
double eps = 1e-12;
#define forn(i, e) for (ll i = 0; i < e; i++)
#define forsn(i, s, e) for (ll i = s; i < e; i++)
#define rforn(i, s) for (ll i = s; i >= 0; i--)
#define rforsn(i, s, e) for (ll i = s; i >= e; i--)
#define ln "\n"
#define dbg(x) cout << #x << " = " << x << ln
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define INF 2e18
#define fast_cin() \
ios_base::sync_with_stdio(false); \
cin.tie(NULL); \
cout.tie(NULL)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
int main()
{
fast_cin();
//ifstream cin("in.txt");
int maxIntervallEnd;
cin >> maxIntervallEnd;
int adamIntervallNum;
cin >> adamIntervallNum;
vector<pair<int, int>> adamIntervalls(adamIntervallNum + 1);
for (int i = 1; i <= adamIntervallNum; i++)
{
cin >> adamIntervalls[i].first >> adamIntervalls[i].second;
}
int eveIntervallNum;
cin >> eveIntervallNum;
vector<pair<int, int>> eveIntervalls(eveIntervallNum + 1);
for (int i = 1; i <= eveIntervallNum; i++)
{
cin >> eveIntervalls[i].first >> eveIntervalls[i].second;
}
int adamPointer = 1;
int evePointer = 1;
int answersNum = 0;
vector<pair<int, int>> answers;
while (adamPointer <= adamIntervallNum && evePointer <= eveIntervallNum)
{
int s = max(adamIntervalls[adamPointer].first, eveIntervalls[evePointer].first);
int f = min(adamIntervalls[adamPointer].second, eveIntervalls[evePointer].second);
if (f - s >= 1)
{
answersNum++;
answers.push_back({s, f});
}
if (adamIntervalls[adamPointer].second < eveIntervalls[evePointer].second)
{
adamPointer++;
}
else //if (adamIntervalls[adamPointer].second > eveIntervalls[evePointer].second)
{
evePointer++;
}
/*else
{
adamPointer++;
evePointer++;
}*/
//cout << adamPointer << " " << evePointer << '\n';
}
cout << answersNum << '\n';
for (int i = 0; i < answersNum; i++)
{
cout << answers[i].first << " " << answers[i].second << '\n';
}
return 0;
}