#include<stdio.h>
#include<string.h>
#include<vector>
using namespace std;

int n,m,e,l[10002],r[10002],f[10002];
vector <int> v[100002];

int cupl(int nod)
{
    int i,nr=v[nod].size();
    if(f[nod])
        return 0;
    f[nod]=1;

    for(i=0;i<nr;++i)
        if(!r[v[nod][i]])
        {
            l[nod]=v[nod][i];
            r[v[nod][i]]=nod;
            return 1;
        }
    for(i=0;i<nr;++i)
        if(cupl(r[v[nod][i]]))
        {
            l[nod]=v[nod][i];
            r[v[nod][i]]=nod;
            return 1;
        }
    return 0;
}

int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    int i,ok=1,nr=0,x,y;

    scanf("%d%d%d",&n,&m,&e);
    for(i=1;i<=e;++i)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    ///////////////////
    ok=1;
    while(ok)
    {
        ok=0;
        memset(f,0,sizeof(f));
        for(i=1;i<=n;++i)
            if(!l[i] && cupl(i))
                ok=1;
    }
    nr=0;
    for(i=1;i<=n;++i)
        if(l[i])
            ++nr;
    printf("%d\n",nr);
    for(i=1;i<=n;++i)
        if(l[i])
            printf("%d %d\n",i,l[i]);


    return 0;
}