#include <cstdio>
#include <vector>

using namespace std;

vector<int> vecini[10005];
int n, m, q;
int viz[10005];
int st[10005];
int dr[10005];

void citire()
{
    scanf("%d %d %d", &n, &m, &q);

    int tmp1, tmp2;

    for(int i = 0; i < q; i++)
    {
        scanf("%d %d", &tmp1, &tmp2);

        vecini[tmp1].push_back(tmp2);
    }
}

int solvex(int x)
{
    if(viz[x] == 1)
    {
        return 0;
    }

    viz[x] = 1;
    int l = vecini[x].size();

    for(int i = 0; i < l; i++)
    {
        if(dr[vecini[x][i]] == 0)
        {
            dr[vecini[x][i]] = x;
            st[x] = vecini[x][i];
            return 1;
        }
        else if(solvex(dr[vecini[x][i]]) == 1)
        {
            dr[vecini[x][i]] = x;
            st[x] = vecini[x][i];
            return 1;
        }
    }

    return 0;
}

void curataViz()
{
    for(int i = 0; i <= n; i++)
    {
        viz[i] = 0;
    }
}

void solve()
{
    bool ok = true;

    while(ok == true)
    {
        ok = false;
        curataViz();

        for(int i = 1; i <= n; i++)
        {
            if(st[i] == 0)
            {
                ok |= solvex(i);
            }
        }
    }

    int nr = 0;

    for(int i = 1; i <= n; i++)
    {
        if(st[i] != 0)
        {
            nr++;
        }
    }

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

    for(int i = 1; i <= n; i++)
    {
        if(st[i] != 0)
        {
            printf("%d %d \n", i, st[i]);
        }
    }
}

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

    citire();
    solve();

    return 0;
}