#include <iostream>
#include <queue>
#define ll long long

using namespace std;

//ifstream cin("a.in");
//ofstream cout("a.out");

struct adat
{
    int k,v;
};

vector <pair<ll,ll>>m;
vector <adat>a,e;

ll n,A,E,i,j;

int main()
{
    cin>>n;

    cin>>A;
    a.resize(A+1);

    for(i=1;i<=A;++i)
    {
        cin>>a[i].k>>a[i].v;
    }

    cin>>E;
    e.resize(E+1);
    for(i=1;i<=E;++i)
    {
        cin>>e[i].k>>e[i].v;
    }

    i=1;
    j=1;

    while(i<=A && j<=E)
    {
        if(e[j].v <= a[i].k) ++j;
        else if(a[i].v <= e[j].k) ++i;
        else if(e[j].k<= a[i].k)
            {
                if(e[j].v>=a[i].v)
                {
                    m.push_back({a[i].k , a[i].v});
                    ++i;
                }
                else
                {
                    m.push_back({a[i].k , e[j].v});
                    ++j;
                }
            }
            else
            {
                if(a[i].v<=e[j].v)
                {
                    m.push_back({e[j].k , a[i].v});
                    ++i;
                }
                else
                {
                    m.push_back({e[j].k , e[j].v});
                    ++j;
                }
            }
    }

    cout<<m.size()<<"\n";
    for(auto &f:m) cout<<f.first<<" "<<f.second<<"\n";

    return 0;
}