#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <utility>
#include <cmath>
#include <string>
#include <cstring>

using namespace std;

bool go(int node, vector<bool> &used, vector<int> &leftnode, vector<int> &rightnode, vector<vector<int>> &g) {
    used[node] = 1;
    for(auto it : g[node]) {
        if(!leftnode[it] || (!used[leftnode[it]] && go(leftnode[it], used, leftnode, rightnode, g))) {
            leftnode[it] = node;
            rightnode[node] = it;
            return 1;
        }
    }
    return 0;
}

int main() {
    ifstream in("cuplaj.in");
    ofstream out("cuplaj.out");

    int n, m, e;
    in >> n >> m >> e;
    vector<vector<int>> g(n + 1);
    for(int i = 1; i <= e; i ++) {
        int x, y;
        in >> x >> y;
        g[x].push_back(y);
    }

    int ok = 1;
    vector<int> leftnode(m + 1, 0);
    vector<int> rightnode(n + 1, 0);
    vector<bool> used(n + 1, 0);
    int ans = 0;
    while(ok) {
        ok = 0;
        for(int i = 1; i <= n; i ++)
            used[i] = 0;
        for(int i = 1; i <= n; i ++)
            if(!used[i] && !rightnode[i])
                ok += go(i, used, leftnode, rightnode, g);
        ans += ok;
    }
    out << ans << "\n";
    for(int i = 1; i <= n; i ++)
        if(rightnode[i])
            out << i << " " << rightnode[i] << "\n";

    return 0;
}