#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const int maxn = 2e5 + 5;
const int inf = 0x3f3f3f3f;

struct edge
{
    int v, next, flow;
}e[maxn << 2];
int head[maxn], tot, s, t;

inline void addedge(int u, int v, int c)
{
    e[++tot] = (edge){v, head[u], c}, head[u] = tot;
    e[++tot] = (edge){u, head[v], 0}, head[v] = tot;
}

int d[maxn], cur[maxn];
bool bfs()
{
    for (int i = s; i <= t; i++) d[i] = 0, cur[i] = head[i];
    queue<int> q; q.push(s);
    while (q.size())
    {
        int u = q.front(); q.pop();
        for (int i = head[u]; ~i; i = e[i].next)
        {
            int v = e[i].v;
            if (!d[v] && e[i].flow)
            {
                d[v] = d[u] + 1;
                if (v == t) return true;
                q.push(v);
            }
        }
    }
    return false;
}

int dfs(int u, int flow)
{
    if (u == t || !flow) return flow;
    int rest = flow;
    for (int i = cur[u]; ~i; i = e[i].next)
    {
        int v = e[i].v;
        if (d[v] == d[u] + 1 && e[i].flow)
        {
            int k = dfs(v, min(rest, e[i].flow));
            if (!k) d[v] = 0;
            e[i].flow -= k, e[i ^ 1].flow += k;
            rest -= k; if (!rest) break;
        }
        cur[u] = i;
    }
    return flow - rest;
}

int Dinic()
{
    int maxflow = 0;
    while (bfs()) maxflow += dfs(s, inf);
    return maxflow;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n1, n2, m;
    cin >> n1 >> n2 >> m;
    s = 0, t = n1 + n2 + 1;
    memset(head, -1, sizeof(head)), tot = -1;
    for (int i = 1; i <= n1; i++) addedge(s, i, 1);
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        cin >> u >> v, u++, v++;
        addedge(u, v + n1, 1);
    }
    for (int i = 1; i <= n2; i++) addedge(i + n1, t, 1);
    cout << Dinic() << "\n";

    for (int i = 0; i <= tot; i += 2)
        if (e[i].v != t && e[i ^ 1].v != s && !e[i].flow) cout << e[i ^ 1].v - 1 << " " << e[i].v - n1 - 1 << "\n";
    return 0;
}