#include <bits/stdc++.h>
using namespace std;
using pii=pair<int,int>;

int main(){
    int p;cin>>p;
    vector<int> dif(p+2);
    int a;cin>>a;
    for(int i=0;i<a;i++){
        int x,y;cin>>x>>y;
        dif[x]++;
        dif[y]--;
    }
    int e;cin>>e;
    for(int i=0;i<e;i++){
        int x,y;cin>>x>>y;
        dif[x]++;
        dif[y]--;
    }
    vector<int> pref(p+1);
    for(int i=1;i<=p;i++){
        pref[i]=pref[i-1]+dif[i];
    }
    vector<pii> ans;
    int i=1;
    while(i<=p){
        int l=i;
        while(l<p&&pref[l]==0)l++;
        if(pref[l]==0)break;
        int r=l;
        while(r<p&&pref[r]>0)r++;
        ans.push_back({l,r});
        i=r+1;
    }
    cout<<ans.size()<<'\n';
    for(auto [x,y]:ans)cout<<x<<' '<<y<<'\n';
}