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

#define NMAX 10005
#define pb push_back

vector<short int> v[NMAX];
char viz[NMAX];
int n,m,k;
short int st[NMAX],dr[NMAX],sol;

int cupleaza(short int nod)
{
    if (viz[nod])
        return 0;        
    viz[nod]=1;
    int i,lim=v[nod].size(),x;
    for(i=0;i<lim;i++)
    {
        x=v[nod][i];
        if(!dr[x])
        {
            st[nod]=x;
            dr[x]=nod;
            return 1;
        }
    }
    for(i=0;i<lim;i++)
    {
        x=v[nod][i];
        if(cupleaza(dr[x]))
        {
            dr[x]=nod;
            st[nod]=x;
            return 1;
        }
    }
    return 0;
}

int main ()
{
    int i,a,b;
    
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d",&n,&m,&k);
    for(i=1;i<=k;i++)
    {
        scanf("%d%d",&a,&b);
        v[a].pb(b);
    }
    
    for(i=1;i<=n;i++)
        if(!st[i])
        {
            if (cupleaza(i))
                ++sol;
            else
            {
                memset(viz,0,sizeof(viz));
                sol+=cupleaza(i);
            }
        }
    printf("%d\n",sol);
    for(i=1;i<=n;i++)
        if(st[i])
            printf("%d %d\n",i,st[i]);
    return 0;
}