#include <cstdio>
#include <vector>

using namespace std;

vector<int> v[10010];
int cup1[10010],cup2[10010];
char vaz[10010];

int cupleaza(int nod)
{
    if(vaz[nod]) return 0;
    vaz[nod]=1;
    for(vector<int>::iterator it=v[nod].begin();it!=v[nod].end();it++)
        if(!cup2[*it] || cupleaza(cup2[*it]))
        {
            cup1[nod]=*it;
            cup2[*it]=nod;
            return 1;
        }
    return 0;
}

int main()
{
    freopen("cuplaj.in", "r", stdin);
    freopen("cuplaj.out", "w", stdout);
    int n,m,q,x,y,ok=1,sol=0;
    scanf("%d%d%d",&n,&m,&q);
    for(int i=1;i<=q;i++)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    while(ok)
    {
        ok=0;
        for(int i=1;i<=n;i++) vaz[i]=0;
        for(int i=1;i<=n;i++)
            if(!cup1[i]) ok|=cupleaza(i);
    }
    for(int i=1;i<=n;i++)
        if(cup1[i]) sol++;
    printf("%d\n",sol);
    for(int i=1;i<=n;i++)
        if(cup1[i]) printf("%d %d\n",i,cup1[i]);
    return 0;
}