#include <bits/stdc++.h>

using namespace std;
int n,a,e,L[100000001],M1[25000001],M2[25000001],m;

int main()
{
    ifstream f("be.in");
    cin>>n>>a;
    for (int i=1; i<=a; i++) {
        int x,y;
        cin>>x>>y;
        for (int j=x; j<y; j++) L[j]++;
    }
    cin>>e;
    for (int i=1; i<=e; i++) {
        int x,y;
        cin>>x>>y;
        for (int j=x; j<y; j++) L[j]++;
    }
    for (int i=1; i<=n; i++) {
        if (L[i]==2) {
            m++;
            M1[m]=i;
            while (L[i]==2 && i<=n) i++;
            M2[m]=i;
        }
    }
    cout<<m<<endl;
    for (int i=1; i<=m; i++) cout<<M1[i]<<" "<<M2[i]<<endl;
    return 0;
}