#include <fstream>
#include <vector>
const int NMAX=100005;

using namespace std;

class InParser
{
    vector<char> str;
    int ptr;
    ifstream fin;

    char getChar()
    {
        if (ptr == int(str.size()))
        {
            fin.read(str.data(), str.size());
            ptr = 0;
        }
        return str[ptr++];
    }

    template<class T>
    T getInt()
    {
        char chr = getChar();
        while (!isdigit(chr) && chr != '-')
            chr = getChar();
        int sgn = +1;
        if (chr == '-')
        {
            sgn = -1;
            chr = getChar();
        }
        T num = 0;
        while (isdigit(chr))
        {
            num = num * 10 + chr - '0';
            chr = getChar();
        }
        return sgn * num;
    }

public:
    InParser(const char* name) : str(1e5), ptr(str.size()), fin(name) { }
    ~InParser()
    {
        fin.close();
    }

    template<class T>
    friend InParser& operator>>(InParser& in, T& num)
    {
        num = in.getInt<T>();
        return in;
    }
};

class OutParser
{
    vector<char> str;
    int ptr;
    ofstream fout;

    void putChar(char chr)
    {
        if (ptr == int(str.size()))
        {
            fout.write(str.data(), str.size());
            ptr = 0;
        }
        str[ptr++] = chr;
    }

    template<class T>
    void putInt(T num)
    {
        if (num < 0)
        {
            putChar('-');
            num *= -1;
        }
        if (num > 9)
            putInt(num / 10);
        putChar(num % 10 + '0');
    }

public:
    OutParser(const char* name) : str(1e5), ptr(0), fout(name) { }
    ~OutParser()
    {
        fout.write(str.data(), ptr);
        fout.close();
    }

    template<class T>
    friend OutParser& operator<<(OutParser& out, const T num)
    {
        out.putInt(num);
        return out;
    }

    friend OutParser& operator<<(OutParser& out, const char chr)
    {
        out.putChar(chr);
        return out;
    }

    friend OutParser& operator<<(OutParser& out, const char* str)
    {
        for (int i = 0; str[i]; i++)
            out.putChar(str[i]);
        return out;
    }
};

InParser fin("cuplaj.in");
OutParser fout("cuplaj.out");

vector <int> v[NMAX];
int cp[NMAX], n, m, ans;
bool viz[NMAX], gasit;

bool cuplaj(int);

int main()
{
    int i, a, b;
    fin>>n>>a>>m;
    for(i=1; i<=m; i++)
    {
        fin>>a>>b;
        b+=n;
        v[a].push_back(b);
    }
    do
    {
        gasit=false;
        for(i=1; i<=n; i++)
        {
            if(!cp[i] && cuplaj(i))
            {
                ans++;
                gasit=true;
            }
        }
        for(i=1; i<=n; i++) viz[i]=false;
    }
    while(gasit);
    fout<<ans<<'\n';
    for(i=1; i<=n; i++)
    {
        if(cp[i]) fout<<i<<' '<<cp[i]-n<<'\n';
    }
    return 0;
}

bool cuplaj(int nod)
{
    if(viz[nod]) return false;
    viz[nod]=true;
    for(auto i:v[nod])
    {
        if(!cp[i])
        {
            cp[i]=nod;
            cp[nod]=i;
            return true;
        }
    }
    for(auto i:v[nod])
    {
        if(cuplaj(cp[i]))
        {
            cp[i]=nod;
            cp[nod]=i;
            return true;
        }
    }
    return false;
}