#include <bits/stdc++.h>

using namespace std;
#ifdef INFOARENA
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
#define cin fin
#define cout fout
#endif // INFOARENA
const int NMAX = 1e4;
vector <int> g[NMAX + 5];
int l[NMAX + 5], r[NMAX + 5];
bool up[NMAX + 5];

bool pairup(int u) {
    if(up[u]) return false;
    up[u] = true;
    for(int v : g[u]) if(!r[v])
        return r[l[u] = v] = u;
    for(int v : g[u]) if(pairup(r[v]))
        return r[l[u] = v] = u;
    return false;
}

int main()
{
    int n, m, e, u, v;
    cin >> n >> m >> e;
    for(int i = 1; i <= e; i++)
        cin >> u >> v,
        g[u].push_back(v);
    for(bool ok = true; ok; ) {
        memset(up, 0, sizeof(up)); ok = false;
        for(int i = 1; i <= n; i++) if(!l[i]) ok |= pairup(i);
    }
    int flow = 0;
    for(int i = 1; i <= n; i++) flow += (l[i] > 0);
    cout << flow << "\n";
    for(int i = 1; i <= n; i++) if(l[i] > 0)
        cout << i << " " << l[i] << "\n";
    return 0;
}