#include<stdio.h>
#include<vector>
using namespace std;
#define nmax 10005
int n, m, nrm, a, b, i, nrp, rez;
vector <int> ma[nmax];
int viz[nmax], st[nmax], dr[nmax];
bool sch;

void citire()
{
    scanf("%ld %ld %ld",&n,&m,&nrm);
    for (i=1;i<=nrm;i++)
    {
        scanf("%ld %ld",&a,&b);
        ma[a].push_back(b);
    }
}

bool pairup(int x)
{
    vector <int> ::iterator it;
    if (viz[x]==nrp)
        return 0;
    viz[x]=nrp;
    for (it=ma[x].begin();it!=ma[x].end();it++)
        if (dr[*it]==0)
        {
            st[x]=*it;  dr[*it]=x;
            return 1;
        }
    for (it=ma[x].begin();it!=ma[x].end();it++)
        if (pairup(dr[*it]))
        {
            st[x]=*it;  dr[*it]=x;
            return 1;
        }
    return 0;
}

void rezolvare()
{
    sch=1;
    while (sch)
    {
        sch=0;
        for (i=1;i<=n;i++)
            if (st[i]==0)
            {
                nrp++;
                if (pairup(i))
                    sch=1;
            }
    }
}

void afisare()
{
    for (i=1;i<=n;i++)
        rez+=(st[i]>0);
    printf("%ld\n",rez);
    for (i=1;i<=n;i++)
        if (st[i]>0)
            printf("%ld %ld\n",i,st[i]);
}

int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    citire();
    rezolvare();
    afisare();
    return 0;
}