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

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

int comb(int nod)
{
    if(u[nod]) return 0;
    u[nod]=1;
    vector<int>::iterator it;

    for(it=m[nod].begin();it!=m[nod].end();it++)
        if(!dr[*it])
        {
            if(!st[nod]) nrcomp++;
            st[nod]=*it;
            dr[*it]=nod;
            return 1;
        }

    for(it=m[nod].begin();it!=m[nod].end();it++)
        if( comb(dr[*it]))
        {
            if(!st[nod]) nrcomp++;
            st[nod]=*it;
            dr[*it]=nod;
            return 1;
        }

    return 0;
}

int main()
{
    int v1,v2,i;
    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 change=1;
    while(change)
    {
        change=0;
        u.reset();
        for(i=1;i<=n1;i++) if(!st[i]) change|=comb(i);
    }
    printf("%d\n",nrcomp);
    for(i=1;i<=n1;i++)
        if(st[i]) printf("%d %d\n",i,st[i]);
    fclose(stdin);
    fclose(stdout);
    return 0;
}