#include <iostream>

using namespace std;

int main()
{
    int P, A, E, x, y;
    int a[P], e[P], p[P];
    cin >> P;
    cin >> A;
    for (int i=0; i<P; i++)
    {
        p[i]=-1;
    }
    for (int i=0; i<P; i++)
    {
        a[i]=-1;
    }
    for (int i=0; i<P; i++)
    {
        e[i]=-1;
    }
    for (int i=0; i<A; i++)
    {
        cin >> x;
        cin >> y;
        x=x+1;
        while (x<=y)
        {
            a[x-1]=x;
            x=x+1;
        }
    }
    cin >> E;
    for (int i=0; i<E; i++)
    {
        cin >> x;
        cin >> y;
        x=x+1;
        while (x<=y)
        {
            e[x-1]=x;
            x=x+1;
        }
    }
    int j=0;
    bool r=0;
    int s;
    for (int i=0; i<P; i++)
    {

        if (a[i]==e[i] and a[i]>-1)
        {
            if (r==0)
            {
                j=j+1;
                r=1;
            }
        }
        else
        {
            if (r==1)
            {
                r=0;
            }
        }
    }
    cout << j << endl;
    r=0;
    for (int i=0; i<P; i++)
    {

        if (a[i]==e[i] and a[i]>-1)
        {
            if (r==0)
            {
                s=a[i]-1;
                cout << s << " ";
                r=1;
            }
            else
            {
                s=s+1;
            }
        }
        else
        {
            if (r==1)
            {
                cout << a[i-1] << endl;
                r=0;
            }
        }
    }
    if (a[P-1]==e[P-1] and a[P-1]>-1 and r==1)
    {
        cout << a[P-1];
    }

    return 0;
}