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

#define pii pair<int, int>
#define se second
#define fi first
#define pb push_back
#define mp make_pair

void solve(){
    int p;
    cin>>p;
    int n, m;
    cin>>n;
    vector<pair<int, int> > a(n);
    for(pair<int, int> &x : a) cin>>x.fi>>x.se;
    cin>>m;
    vector<pii> b(m);
    for(pair<int, int> &x : b) cin>>x.fi>>x.se;
    int i=0, j=0;
    vector<pii> ans;
    while(i<n && j<m){
        if(a[i].fi<=b[j].fi){
            if(b[j].fi<a[i].se){
                ans.pb(mp(b[j].fi, a[i].se));
            }
            i++;
        }
        else{
            if(a[i].fi<b[j].se){
                ans.pb(mp(a[i].fi, b[j].se));
            }
            j++;
        }
    }
    cout<<ans.size()<<"\n";
    for(pii x : ans) cout<<x.first<<" "<<x.second<<"\n";
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    solve();
}