#include<bits/stdc++.h>
using namespace std;

typedef pair<int,int> pii;
#define mp make_pair
#define fir first
#define sec second
const int maxn=5e5+10;
const int inf=2e9;

inline int read(){
    int x=0,w=1;char c=getchar();
    while(c<'0'||c>'9'){if(c=='-')w=-1;c=getchar();}
    while(c<='9'&&c>='0'){x=(x<<3)+(x<<1)+c-'0';c=getchar();}
    return x*w;
}

int n,L,R;
struct Segment{
    int id,x1,y1,x2,y2;
    Segment()=default;
    Segment(int id_,int x1_,int y1_,int x2_,int y2_):id(id_),x1(x1_),y1(y1_),x2(x2_),y2(y2_){}
    //(Y-y1)/(X-x1)=(y2-y1)/(x2-x1) Y(x2-x1)=(y2-y1)(X-x1)+y1(x2-x1) 
    bool operator<(const Segment& rhs)const{
        if(x1<rhs.x1) return 1ll*(y2-y1)*(rhs.x1-x1)+1ll*y1*(x2-x1)<1ll*rhs.y1*(x2-x1);
        else return 1ll*y1*(rhs.x2-rhs.x1)<1ll*(rhs.y2-rhs.y1)*(x1-rhs.x1)+1ll*rhs.y1*(rhs.x2-rhs.x1);
    }
}Seg[maxn];
struct Data{
    int id,val;
    Data()=default;
    Data(int id_,int val_):id(id_),val(val_){}
    bool operator<(const Data& rhs)const{
        return val>rhs.val;
    }
};
set<Segment> S;
priority_queue<Data> Q;
vector<int> E[maxn];
int deg[maxn];
queue<int> q;
multiset<pii> Sp,Sn;
inline void output(){
    printf("~~~~ Sp ~~~~\n");
    for(auto it:Sp) printf("%d %d\n",it.fir,it.sec);
    printf("~~~~ Sn ~~~~\n");
    for(auto it:Sn) printf("%d %d\n",it.fir,it.sec);
}
int main(){
    // freopen("rain.in","r",stdin);
    // freopen("rain.out","w",stdout);
    L=read()*2,R=read()*2,n=read();
    for(int i=1;i<=n;++i){
        int x1=read()*2,y1=read(),x2=read()*2,y2=read();
        if(x1>x2) swap(x1,x2),swap(y1,y2);
        Seg[i]=Segment(i,x1,y1,x2,y2);
    }
    sort(Seg+1,Seg+n+1,[&](Segment A,Segment B){
        return A.x1<B.x1;
    });
    for(int i=1;i<=n;++i) Seg[i].id=i;
    // for(int i=1;i<=n;++i) printf("id:%d (%d,%d) (%d,%d)\n",Seg[i].id,Seg[i].x1,Seg[i].y1,Seg[i].x2,Seg[i].y2);
    for(int i=1;i<=n;++i){
        while(!Q.empty()&&Q.top().val<Seg[i].x1){
            S.erase(Seg[Q.top().id]);
            Q.pop();
        }
        auto it=S.lower_bound(Seg[i]);
        if(it!=S.end()){
            E[(*it).id].push_back(i);
            ++deg[i];
        }
        if(it!=S.begin()){
            --it;
            E[i].push_back((*it).id);
            ++deg[(*it).id];
        }
        S.insert(Seg[i]);
        Q.push(Data(i,Seg[i].x2));
    }
    for(int i=1;i<=n;++i){
        if(!deg[i]) q.push(i);
    }
    Sp.insert(mp(R+1,inf));
    Sn.insert(mp(L,inf));
    while(!q.empty()){
        int u=q.front();
        q.pop();
        // output();
        if(Seg[u].y1<Seg[u].y2){
            auto it1=Sn.lower_bound(mp(Seg[u].x2+1,-inf));
            if(it1!=Sn.begin()){
                --it1;
                while((*it1).fir>=Seg[u].x1+1){
                    int val=(*it1).sec;
                    auto it2=Sp.lower_bound(mp((*it1).fir+1,-inf));
                    if(it2!=Sp.begin()){
                        --it2;
                        while(val&&(*it2).fir>=Seg[u].x1){
                            if((*it2).sec>val){
                                Sp.insert(mp((*it2).fir,(*it2).sec-val));
                                Sp.erase(it2);
                                val=0;
                                break;
                            }
                            else{
                                val-=(*it2).sec;
                                auto tmp=it2;
                                if(it2!=Sp.begin()){
                                    --it2;
                                    Sp.erase(tmp);
                                }
                                else{
                                    Sp.erase(tmp);
                                    break;
                                }
                            }
                        }
                    }   
                    if(val) Sn.insert(mp(Seg[u].x1,val));
                    auto tmp=it1;
                    if(it1!=Sn.begin()){
                        --it1;
                        Sn.erase(tmp);
                    }
                    else{
                        Sn.erase(tmp);
                        break;
                    }
                }
            }
            Sp.insert(mp(Seg[u].x1+1,1));
            Sn.insert(mp(Seg[u].x2+1,1));
        }
        else{
            auto it1=Sp.lower_bound(mp(Seg[u].x1,-inf));
            while(it1!=Sp.end()&&(*it1).fir<=Seg[u].x2){
                int val=(*it1).sec;
                auto it2=Sn.lower_bound(mp((*it1).fir,-inf));
                while(it2!=Sn.end()&&val&&(*it2).fir<=Seg[u].x2+1){
                    if((*it2).sec>val){
                        Sn.insert(mp((*it2).fir,(*it2).sec-val));
                        Sn.erase(*it2);
                        val=0;
                        break;
                    }
                    else{
                        val-=(*it2).sec;
                        auto tmp=it2;
                        ++it2;
                        Sn.erase(tmp);
                        if(it2==Sn.end()) break;
                    }
                }
                if(val) Sp.insert(mp(Seg[u].x2+1,val));
                auto tmp=it1;
                ++it1;
                Sp.erase(tmp);
            }
            Sp.insert(mp(Seg[u].x1,1));
            Sn.insert(mp(Seg[u].x2,1));
        }
        for(int v:E[u]){
            --deg[v];
            if(!deg[v]) q.push(v);
        }
    }
    for(auto it=Sn.begin();it!=Sn.end();++it){
        Sp.insert(mp((*it).fir,-(*it).sec));
    }
    // for(auto it=Sp.begin();it!=Sp.end();++it){
    //     printf("%d %d\n",(*it).fir,(*it).sec);
    // }
    int ans=inf,sum=inf,now=-inf;
    Sp.insert(mp(L,0));
    for(auto it=Sp.begin();it!=Sp.end();++it){
        if((*it).fir!=now&&now>=L&&now<=R) ans=min(ans,sum);
        now=(*it).fir,sum+=(*it).sec;
    }
    printf("%d\n",ans);
    return 0;
}