#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define ld long double
#define chad char
#define mod 5000011
#define dim 100005
#define lim 1000000
#define INF 1000000000
#define FOR(i,a,b) for(int i=(a); i<=(b); i++)
#define piii pair<int,pair<int,int> > 
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define mp make_pair
#define nr_biti __builtin_popcount
using namespace std;
 
ifstream fin("cuplaj.in");    
ofstream fout("cuplaj.out"); 

int n1,n2,m;
vector<int> g[dim];

struct cuplaj
{
    vector<int> st;
    vector<int> dr;
    vector<bool> viz;
    int n1,n2;
    int ans;

    void init(int _n1,int _n2)
    {
        this->n1=_n1;
        this->n2=_n2;
        this->st=vector<int>(_n2+3,0);
        this->dr=vector<int>(_n1+3,0);
        this->viz=vector<bool>(_n1+3,0);
        this->ans=0;
        return;
    }

    bool dfs(int nod)
    {
        if(viz[nod])
            return 0;

        viz[nod]=1;

        for(auto it:g[nod])
        {
            if(!st[it])
            {
                st[it]=nod;
                dr[nod]=it;
                return 1;
            }
        }

        for(auto it:g[nod])
        {
            if(dfs(st[it]))
            {
                st[it]=nod;
                dr[nod]=it;
                return 1;
            }
        }

        return 0;
    }

    void cauta_cuplaj()
    {
        while(1)
        {
            bool sch=0;

            for(int i=1; i<=n1; i++)
                viz[i]=0;

            for(int i=1; i<=n1; i++)
            {
                if(!dr[i])
                    sch|=dfs(i);
            }

            if(!sch)
                break;
        }

        for(int i=1; i<=n1; i++)
            ans+=(dr[i]>0);
    }

    void afis()
    {
        fout << ans << "\n";

        for(int i=1; i<=n1; i++)
            if(dr[i])
                fout << i << " " << dr[i] << "\n";
    }
};

int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(nullptr);
    fout.tie(nullptr); 

    fin >> n1 >> n2 >> m;

    for(int i=1; i<=m; i++)
    {
        int x,y;

        fin >> x >> y;

        g[x].pb(y);
    }

    cuplaj alfa;

    alfa.init(n1,n2);
    alfa.cauta_cuplaj();
    alfa.afis();

    return 0;
}