#include <fstream>
#include <iomanip>
#include <algorithm>
#include <vector>
#include <cassert>
#include <cmath>
#include <stack>
#include <set>
#include <functional>
#include <bitset>
#include <map>
#include <unordered_map>
#include <queue>
#include <array>
#include <numeric>
#include <complex>
using namespace std;
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename A> ostream& operator<<(ostream& os, vector<A>& a) { for(auto &c:a)os<<c<<' '; return os;}
template<typename A> istream& operator>>(istream& os, vector<A>& a) { for(auto &c:a)os>>c; return os;}
template<typename A,size_t N> istream& operator>>(istream &os, array<A,N>&a) { for(auto &c:a)os>>c; return os;}
template<typename A,typename B> istream& operator>>(istream& os, pair<A,B>&a) { os>>a.first>>a.second; return os;}
template<typename A> istream& operator >>(istream& os,complex<A>& a){pair<A,A>aux;os>>aux;a=complex<A>(aux.first,aux.second);return os;}
#define bug(a) cerr << "(" << #a << ": " << a << ")\n";
#define all(x) x.begin(),x.end()
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define PQ priority_queue
#define x real
#define y imag
using pii= pair<int,int>;
using VI= vector<int>;
using v64= vector<int64_t>;
using point=complex<double>;
using i64= int64_t;
using i16= int16_t;
using u64= uint64_t;
using u32= uint32_t;
using i32= int32_t;
using u16= uint16_t;
const i64 inf=1e18;
const i64 INF=1e18;
const int mod=1e9+9;
ifstream cin("cuplaj.in");
ofstream cout("cuplaj.out");
void solve()
{
    int n,m,q;
    cin>>n>>m>>q;
    vector<vector<int>>g(n);
    while(q--)
    {
        int x,y;
        cin>>x>>y;
        g[x-1].pb(y-1);
    }
    vector<int>l(n,-1),r(m,-1);
    vector<int>viz(n);


    function<bool(int)>dfs=[&](int nod)
    {
        if(viz[nod])
            return false;
        viz[nod]=1;
        for(auto &c:g[nod])
        {
            if(r[c]==-1)
            {
                l[nod]=c;
                r[c]=nod;
                return true;
            }
        }
        for(auto &c:g[nod])
        {
            if(dfs(r[c]))
            {
                l[nod]=c;
                r[c]=nod;
                return true;
            }
        }
        return false;
    };

    for(bool ok=1;ok;)
    {
        ok=0;
        fill(all(viz),0);
        for(int i=0;i<n;i++)
        {
            if(l[i]==-1)
                ok|=dfs(i);
        }
    }
    int rez=0;
    for(int i=0;i<n;i++)
    {
        if(l[i]!=-1)
            rez++;
    }
    cout<<rez<<'\n';
    for(int i=0;i<n;i++)
    {
        if(l[i]!=-1)
            cout<<i+1<<' '<<l[i]+1<<'\n';
    }
}
main()
{
    i32 tt=1;
    ios::sync_with_stdio(false);
    cin.tie(0);
    //cin>>tt;
    while(tt--)
    {
        solve();
    }
}