#include <algorithm>
#include <fstream>
#include <vector>
#include <utility>

using namespace std;

const int nmax = 1e4;

ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");

int n, k, e, u, v;
vector<int> g[nmax+1], mt, l;
vector<bool> used;

bool try_kuhn(int v) {
    if(used[v])
        return false;
    used[v] = true;

    for(int to : g[v]) {
        if(mt[to] == -1 || try_kuhn(mt[to])) {
            l[v] = to;
            mt[to] = v;
            return true;
        }
    }

    return false;
}

int main() {
    fin >> n >> k >> e;
    while(e--) {
        fin >> u >> v;
        --u, --v;
        g[u].push_back(v);
    }

    mt.assign(k, -1);

    int change = 1;
    l.assign(n, -1);
    while(change){
        change = 0;
        used.assign(n, false);
        for (int v = 0; v < n; ++v) {
            if (l[v] == -1){
                change |= try_kuhn(v);
            }
        }
    }

    vector<pair<int, int>> ans;
    for(int i=0; i<k; i++) {
        if(mt[i] != -1) {
            ans.emplace_back(mt[i]+1, i+1);
        }
    }

    sort(ans.begin(), ans.end());
    fout << ans.size() << '\n';
    for (auto it : ans){
        fout << it.first << ' ' << it.second << '\n';
    }

    return 0;
}