#include <fstream>
#include <string.h>
#include <vector>
#include <queue>
#include <limits.h>

#define nMax 100001
#define lgMax 19
#define pb push_back
#define INF INT_MAX
#define bit(i) i&(-i)
using namespace std;
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
int L, R, m, cuplaj;
int viz[nMax], l[nMax], r[nMax];
vector<int> G[nMax];
void read()
{
    int a, b;
    fin>>L>>R>>m;

    for(int i=1;i<=m;i++)
    {
        fin>>a>>b;
        G[a].pb(b);
    }
}
inline bool pairup(int node)
{
    if(viz[node])
        return 0;
    viz[node]=1;

    for(vector<int>::iterator it=G[node].begin();it!=G[node].end();it++)
    {
        int fiu=*it;
        if(r[fiu]==0)
        {
            cuplaj++;
            r[fiu]=node;
            l[node]=fiu;
            return 1;
        }
    }

    for(vector<int>::iterator it=G[node].begin();it!=G[node].end();it++)
    {
        int fiu=*it;
        if(pairup(r[fiu]))
        {
            r[fiu]=node;
            l[node]=fiu;
            return 1;
        }
    }

    return 0;
}
void solve()
{
    for(int change=1;change;)
    {
        change=0;
        memset(viz, 0, sizeof(viz));
        for(int i=1;i<=L;i++)
            if(l[i]==0)
                change |= pairup(i);
    }
}
void write()
{
    fout<<cuplaj<<'\n';

    for(int i=1;i<=L;i++)
        if(l[i])
            fout<<i<<" "<<l[i]<<'\n';
}
int main()
{
    read();
    solve();
    write();
    return 0;
}