#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
#include <algorithm>
#include <cstring>
#include <cctype>

#define pb push_back
#define mp make_pair
#define MAXN 500001
#define DIM 8192
#define INFILE "cuplaj.in"
#define OUTFILE "cuplaj.out"

using namespace std;

class Reader
{
public:
    Reader(const char* filename)
    {
        f.open(filename);
        pos = 0;
        f.read(buffer,DIM);
    }
    inline Reader& operator >>(int& x)
    {
        x=0;
        sgn=1;
        while((buffer[pos]<'0'||buffer[pos]>'9')&&buffer[pos]!='-')
            if(++pos==DIM)
                f.read(buffer,DIM),pos=0;
        if(buffer[pos]=='-')sgn=-1,pos++;
        while(buffer[pos]>='0'&&buffer[pos]<='9')
        {
            x=x*10+buffer[pos]-'0';
            if(++pos==DIM)f.read(buffer,DIM),pos=0;
        }
        x*=sgn;
        return (*this);
    }
    inline Reader& operator >>(char* c)
    {
        aux = 0;
        while(isspace(buffer[pos]))
            if(++pos==DIM)
                f.read(buffer,DIM),pos=0;
        while(!isspace(buffer[pos]))
        {
            c[aux++]=buffer[pos];
            if(++pos==DIM)f.read(buffer,DIM),pos=0;
        }
        return (*this);
    }
    ~Reader()
    {
        f.close();
    }
private:
    ifstream f;
    int pos,aux,sgn;
    char buffer[DIM];
};

class Writer
{
public:
    Writer(const char* filename)
    {
        g.open(filename);
        pos = 0;
    }
    inline Writer& operator <<(int xx)
    {
        aux = 0;
        x = xx;
        if(xx<0)x=-x;
        if(x==0)
            nr[aux++]='0';
        while(x)
        {
            nr[aux++]=x%10+'0';
            x/=10;
        }
        if(xx<0)nr[aux++]='-';
        while(aux>0)
        {
            buffer[pos++]=nr[--aux];
            if(pos==DIM)g.write(buffer,DIM),pos=0;
        }
        return (*this);
    }
    inline Writer& operator <<(const char* c)
    {
        aux = 0;
        while(c[aux])
        {
            buffer[pos++]=c[aux++];
            if(pos==DIM)g.write(buffer,DIM),pos=0;
        }
        return (*this);
    }
    ~Writer()
    {
        g.write(buffer,pos);
        g.close();
    }
private:
    ofstream g;
    int pos,aux,x;
    char buffer[DIM],nr[21];
};

Reader f(INFILE);
Writer g(OUTFILE);

int n,m,cnt,l[10001],r[10001],a,b;
bitset<100001> use;
vector<int> G[10001];
int pairup(int n)
{
    if(use[n])return 0;
    use[n]=1;
    vector<int>::iterator it;
    for(it=G[n].begin();it!=G[n].end();++it)
        if(!r[*it]||pairup(r[*it]))
        {
            l[n]=*it;
            r[*it]=n;
            return 1;
        }
    return 0;
}
int main()
{
    f>>n>>m>>cnt;
    for(;cnt--;)
    {
        f>>a>>b;
        G[a].push_back(b);
    }
    int cuplaj=0;
    for(int i=1;i<=n;i++)
        if(!l[i])
        {
            if(!pairup(i))
            {
                use.reset();
                cuplaj+=pairup(i);
            }
            else cuplaj++;
        }
    g<<cuplaj<<"\n";
    for(int i=1;i<=n;i++)
        if(l[i])g<<i<<" "<<l[i]<<"\n";
    return 0;
}