#include <fstream>
#include <vector>
#include <cstring>
#define NMAX 10005

using namespace std;

typedef vector<int>::iterator iter;
FILE* f=freopen("cuplaj.in","r",stdin);
FILE* o=freopen("cuplaj.out","w",stdout);

int nr,nl,n;
vector<int> graph[NMAX];
bool used[NMAX];
int lft[NMAX],rgt[NMAX];
int couples;

void Reading()
{
    scanf("%d%d%d",&nl,&nr,&n);
    for(int i=0;i<n;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        graph[x].push_back(y);
    }
}

int Match(int x)
{
    if(used[x])
        return 0;
    used[x]=1;
    for(iter i=graph[x].begin();i<graph[x].end();++i)
    {
        if(!rgt[*i])
        {
            rgt[*i]=x;
            lft[x]=*i;
            return 1;
        }
    }
    for(iter i=graph[x].begin();i<graph[x].end();++i)
    {
        if(Match(rgt[*i]))
        {
            rgt[*i]=x;
            lft[x]=*i;
            return 1;
        }
    }
    return 0;
}

int main()
{
    Reading();
    int ok=1;
    while(ok)
    {
        ok=0;
        memset(used,0,sizeof(used));
        for(int i=1;i<=nl;++i)
        {
            if(!lft[i])
            {
                ok |= Match(i);
            }
        }
    }

    for(int i=1;i<=nl;++i)
    {
        if(lft[i])
            couples+=1;
    }
    printf("%d\n",couples);
    for(int i=1;i<=nl;++i)
    {
        if(lft[i])
            printf("%d %d\n",i,lft[i]);
    }

    return 0;
}