#include <bits/stdc++.h>

using namespace std;
#define pb push_back
#define sz(x) (int)(x.size())
const int N = 1e4 + 5;

int n, m, e, mt[N], l[N];
bool used[N];
vector<int> g[N];

bool cuplaj(int node) {
    if (used[node] == true)
        return false;
    used[node] = true;
    for (auto it : g[node]) {
        if (mt[it] == -1 || cuplaj(mt[it])) {
            mt[it] = node;
            l[node] = it;
            return true;
        }
    }
    return false;
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    freopen("cuplaj.in", "r", stdin);
    freopen("cuplaj.out", "w", stdout);
    cin >> n >> m >> e;
    for (int i = 1; i <= e; i++) {
        int u, v;
        cin >> u >> v;
        g[u].pb(v);
    }
    for (int i = 1; i <= n; i++) {
        l[i] = -1;
    }
    for (int i = 1; i <= m; i++) {
        mt[i] = -1;
    }

    bool change = 1;
    while (change) {
        change = 0;
        memset(used, false, sizeof(used));
        for (int v = 1; v <= n; v++) {
            if (l[v] == -1) {
                change |= cuplaj(v);
            }
        }
    }
    vector<pair<int, int>> ans;
    for (int i = 1; i <= m; i++) {
        if (mt[i] != -1) {
            ans.pb({mt[i], i});
        }
    }
    sort(ans.begin(), ans.end());
    cout << sz(ans) << '\n';
    for (auto it : ans) {
        cout << it.first << ' ' << it.second << '\n';
    }
}