#include <iostream>
#include <cstdio>
#include <vector>
#include <bitset>
using namespace std;

int n1,n2,m1,st[10005],dr[10005];
vector<int> m[10005];
bitset<10005> u;
int nrcomb;

int comb(int nod)
{
    if(u[nod]==1) return 0;
    u[nod]=1;

    for(vector<int>::iterator it=m[nod].begin();it!=m[nod].end();it++)
        if(!dr[*it])
        {
            dr[*it]=nod;
            st[nod]=*it;
            nrcomb++;
            return 1;
        }

    for(vector<int>::iterator it=m[nod].begin();it!=m[nod].end();it++)
        if( comb(dr[*it]))
        {
            dr[*it]=nod;
            st[nod]=*it;
            return 1;
        }

    return 0;
}

int main()
{
    int p1,p2,i;
    freopen("cuplu.in","r",stdin);
    freopen("cuplu.out","w",stdout);
    scanf("%d%d%d",&n1,&n2,&m1);
    for(;m1;m1--)
    {
        scanf("%d%d",&p1,&p2);
        m[p1].push_back(p2);
    }
    int change=1;
    while(change)
    {
        u.reset(); change=0;
        for(i=1;i<=n1;i++)
            if(!st[i])
                change|=comb(i);
    }
    printf("%d\n",nrcomb);
    for(i=1;i<=n1;i++)
        if(st[i]) printf("%d %d\n",i,st[i]);
    fclose(stdin);
    fclose(stdout);
    return 0;
}