#include <iostream>
//#include <fstream>
#include <vector>

using namespace std;

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

vector<int>x;

vector<pair<int,int> >v;

int i,n,a,e,p,q,db,maxi;

int main()
{
    cin>>n;
    cin>>a;
    x.resize(n+1);
    for(i=1;i<=a;++i)
    {
        cin>>p>>q;
        x[p]++;
        x[q]--;
    }
    cin>>e;
    for(i=1;i<=e;++i)
    {
        cin>>p>>q;
        x[p]++;
        x[q]--;
    }

    for(i=1;i<=n;++i)
        x[i]+=x[i-1];

    for(i=1;i<=n;++i)
    {
        if(x[i]==2) db++;
        else if(db!=0)
        {
            v.push_back({i-db,i});
            db=0;
        }
    }
    cout<<v.size()<<"\n";
    for(auto e:v)
        cout<<e.first<<" "<<e.second<<"\n";
    return 0;

}