#include <iostream>
#include <cstdio>
#include <vector>
#include <cstring>
#define nmax 10005
using namespace std;

int n,m,l,st[nmax],dr[nmax],viz[nmax];
vector <int > graf[nmax];

int cuplez(int nod)
{
    if (viz[nod])
        return 0;
    viz[nod]=1;
    for (vector <int > :: iterator it = graf[nod].begin(); it!=graf[nod].end(); ++it)
        if (!dr[*it])
        {
            dr[*it]=nod;
            st[nod]=*it;
            return 1;
        }
    for (vector <int > :: iterator it = graf[nod].begin(); it!=graf[nod].end(); ++it)
        if (cuplez(dr[*it]))
        {
            st[nod]=*it;
            dr[*it]=nod;
            return 1;
        }
    return 0;
}

int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d",&n,&m,&l);
    for (int i=1; i<=l; ++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        graf[x].push_back(y);
    }
    for (int i=1; i<=n; ++i)
        for (vector <int > :: iterator it = graf[i].begin(); it!=graf[i].end(); ++it)
            if (!dr[*it])
            {
                dr[*it]=i;
                st[i]=*it;
                break;
            }
    int ok=1;
    while (ok)
    {
        ok=0;
        memset(viz,0,sizeof(viz));
        for (int i=1; i<=n; ++i)
            if (!st[i])
            {
                ok+=cuplez(i);
            }
    }
    int sum=0;
    for (int i=1;i<=n;++i)
        if (st[i])
            ++sum;
    printf("%d\n",sum);
    for (int i=1;i<=n;++i)
        if (st[i])
            printf("%d %d\n",i,st[i]);
    return 0;
}