#include <iostream>
#include<vector>
#include<map>

using namespace std;

int const c=100000;
int n,adam,eva,a,b,szamlalo=0;
vector<vector<int> > nums;
vector<vector<int> > ki;

int main()
{
    cin>>n;
    nums.assign(100,vector<int>(100001,0));
    cin>>adam;
    while(adam--)
    {
        cin>>a>>b;
        nums[a/c][a%(c+1)]++;
        nums[b/c][b%(c+1)]--;
    }
    cin>>adam;
    while(adam--)
    {
        cin>>a>>b;
        nums[a/c][a%(c+1)]++;
        nums[b/c][b%(c+1)]--;
    }
    /*for(int i=0;i*c<=n;i++)
    {
        for(int j=1;j<=c;j++)
        {
            szamlalo+=nums[i][j];
            if(szamlalo==2 && nums[i][j]>0)
            {
               ki.push_back({i*c+j});
               continue;
            }
            if((szamlalo==1 && nums[i][j]==-1) || (szamlalo==0 && nums[i][j]==-2))
            {
                ki.back().push_back(i*c+j);
                continue;
            }
        }
    }*/
    cout<<ki.size()<<"\n";
    for(auto x:ki) cout<<x[0]<<" "<<x[1]<<"\n";
    return 0;
}