#include <fstream>
#include <cstring>
#include <vector>
using namespace std;

const int N = 1 + 1e5;

vector<int> adj[N];
int match[N], pairof[N], nA, nB;
bool use[N];


bool pairup(int x){
    if ( use[x] ) return false;
    use[x] = true;

    for (int y : adj[x])
        if ( pairof[y] == -1 ){
            match[x] = y;
            pairof[y] = x;
            return true;
        }
    for (int y : adj[x])
        if ( pairup( pairof[y] ) ){
            match[x] = y;
            pairof[y] = x;
            return true;
        }
    return false;
}
int maxMatch(){
    memset(match, -1, sizeof(match));
    memset(pairof, -1, sizeof(pairof));
    bool go;
    do {
        memset(use, false, sizeof(use));
        go = false;
        for (int i = 1; i <= nA; i++)
            if ( match[i] == -1 )
                go |= pairup(i);
    } while (go);
}

int main(){
    ifstream in("cuplaj.in");
    ofstream out("cuplaj.out");
    int times, x, y;

    in >> nA >> nB >> times;
    while (times--){
        in >> x >> y;
        adj[x].push_back(y);
    }

    maxMatch();
    int ans = 0;
    for (int i = 1; i <= nA; i++)
        ans += match[i] != -1;
    out << ans << '\n';

    for (int i = 1; i <= nA; i++)
        if ( match[i] != -1 )
            out << i << ' ' << match[i] << '\n';
    return 0;
}