#include <cstdio>
#include <vector>
#include <cstring>

#define MAXN 10001
#define INF 0x3f3f3f3f

using namespace std;

vector <int> G[MAXN];

int n, m, q[MAXN], u[MAXN], v[MAXN];
bool vis[MAXN];

bool pair_up(int node)
{
    if(vis[node]) return 0;

    unsigned int i;

    vis[node] = 1;
    for(i=0; i<G[node].size(); ++i)
    {
        if(v[G[node][i]] == 0)
        {
            u[node] = G[node][i];
            v[G[node][i]] = node;
            return 1;
        }
    }

    for(i=0; i<G[node].size(); ++i)
        if(pair_up(v[G[node][i]]))
        {
            v[G[node][i]] = node;
            u[node] = G[node][i];
            return 1;
        }

    return 0;
}

int main()
{
    freopen("cuplaj.in", "r", stdin);
    freopen("cuplaj.out", "w", stdout);

    int i, x, y, edges, ans = 0, f;

    scanf("%d%d%d", &n, &m, &edges);

    for(i=1; i<=edges; ++i)
    {
        scanf("%d%d", &x, &y);
        G[x].push_back(y);
    }

    f = 1;
    while(f)
    {
        f = 0;
        memset(vis, 0, sizeof vis);
        for(i=1; i<=n; ++i)
            if(!u[i])
                if(pair_up(i))
                    f = 1;
    }

    for(i=1; i<=n; ++i)
        if(u[i])
            ans++;

    printf("%d\n", ans);

    for(i=1; i<=n; ++i)
        if(u[i])
            printf("%d %d\n", i, u[i]);

    return 0;
}