#include <fstream>
#include <vector>
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;
    }
};

const int MAX = 1e4 + 1;

vector <int> g[MAX];

int a , b , m , l[MAX] , r[MAX] , cuplaj;

bool viz[MAX];

int cupleaza( int i ){

    viz[i] = 1;

    for(auto it:g[i]){

        if(!r[it]){

            r[it] = i;
            l[i] = it;
            return 1;
        }
    }

    for(auto it:g[i]){

        if(!viz[r[it]] && cupleaza(r[it])){

            r[it] = i;
            l[i] = it;
            return 1;
        }
    }

    return 0;
}

int main(){

    InParser cin("cuplaj.in");
    OutParser cout("cuplaj.out");

    cin >> a >> b >> m;

    int x , y;

    while(m--){

        cin >> x >> y;

        g[x].push_back(y);
    }

    bool ok = 1;

    while(ok){

        ok = 0;

        for(int i = 1 ; i <= a ; i++){

            viz[i] = 0;
        }

        for(int i = 1 ; i <= a ; i++){

            if(!l[i] && cupleaza(i)){

                cuplaj++;

                ok = 1;
            }
        }
    }

    cout << cuplaj << '\n';

    for(int i = 1 ; i <= a ; i++){

        if(l[i]) cout << i << ' ' << l[i] << '\n';
    }

    return 0;
}