#include <iostream>
#include <cstdio>
#include <vector>
#define nmax 10005
#define pb push_back
using namespace std;

int st[nmax],dr[nmax],u[nmax];
int n1,n2,m1,nrnod=0;
vector<int> m[nmax];

int mpair(int nod)
{
    int i;
    if(u[nod]) return 0;
    u[nod]=1;
    for(i=0;i<m[nod].size();i++)
        if(!dr[m[nod][i]])
        {
            if(st[nod]==0) nrnod++;
            st[nod]=m[nod][i];
            dr[m[nod][i]]=nod;
            return 1;
        }
    for(i=0;i<m[nod].size();i++)
        if(mpair(dr[m[nod][i]]))
        {
            if(st[nod]==0) nrnod++;
            st[nod]=m[nod][i];
            dr[m[nod][i]]=nod;
            return 1;
        }
    return 0;
}

int main()
{
    int v1,v2;
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d",&n1,&n2,&m1);
    for(;m1;m1--)
    {
        scanf("%d%d",&v1,&v2);
        m[v1].pb(v2);
    }
    int i,change=1;
    while(change)
    {
        change=0;
        for(i=1;i<=n1;i++) u[i]=0;
        for(i=1;i<=n1;i++)
            if(!st[i]) change|=mpair(i);
    }
    printf("%d\n",nrnod);
    for(i=1;i<=n1;i++) if(st[i]) printf("%d %d\n",i,st[i]);
    fclose(stdin);
    fclose(stdout);
    return 0;
}