#include<stdio.h>
#include<vector>
#include<algorithm>

using namespace std;

#define Nmax 10005

vector <int> l[Nmax];

int N,M,p[Nmax],r[Nmax],v[Nmax];

int pairup(int k)
{
    if (v[k])
        return 0;
    v[k]=1;
    for(int i=0;i<(int)l[k].size();++i)
        if (!r[ l[k][i] ])
            {
            p[k] = l[k][i];
            r[l[k][i]]=k;
            return 1;
            }
    for(int i=0;i<(int)l[k].size();++i)
        if (r[l[k][i]]!=k && pairup(r[ l[k][i] ]))
            {
            p[k] = l[k][i];
            r[l[k][i]]=k;
            return 1;
            }
    return 0;
}

void solve()
{
    for(int ok=1 ; ok ; )
        {
        ok=0;
        memset(v,0,sizeof(v));
        for(int i=1;i<=N;++i)
            if (!p[i])
                ok |= pairup(i);
        }

    int cnt=0;
    for(int i=1;i<=N;++i)
        if (p[i])
            cnt++;
    printf("%d\n",cnt);

    for(int i=1;i<=N;++i)
        if (p[i])
            printf("%d %d\n",i,p[i]);
}

void cit();

int main()
{
    cit();
    solve();
    return 0;
}

void cit()
{
    int a,b,e;
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d",&N,&M,&e);
    for(int i=1;i<=e;++i)
        {
        scanf("%d%d",&a,&b);
        l[a].push_back(b);
        }
}