#include <fstream>
#include <cstdio>
#include <vector>
#include <cstring>
#define Nmax 10000
using namespace std;

ofstream g("cuplaj.out");

vector<int> A[Nmax+1];
int n,m,e,l[Nmax+1],r[Nmax+1];
bool uz[Nmax+1];

bool cupleaza(int nod)
{
    uz[nod] = 1;
    for (int i=0;i<A[nod].size();i++)
    {
        int crt = A[nod][i];
        if(!r[crt])
        {
            r[crt] = nod;
            l[nod] = crt;
            return 1;
        }
    }

    for (int i=0;i<A[nod].size();i++)
    {
        int crt = A[nod][i];
        if (!uz[r[crt]] && cupleaza(r[crt]))
        {
            r[crt] = nod;
            l[nod] = crt;
            return 1;
        }
    }
    return 0;
}

int main()
{
    freopen("cuplaj.in","r",stdin);

    scanf("%d%d%d",&n,&m,&e);

    for (int i=1;i<=e;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        A[x].push_back(y);
    }

    bool change;
    do
    {
        change = 0;
        memset(uz,0,sizeof(uz));
        for (int i=1;i<=n;i++)
        {
            if (!l[i])
                change |= cupleaza(i);
        }
    }while (change);

    int nr=0;
    for (int i=1;i<=n;i++)
    {
        if (l[i])
            nr++;
    }

    g<<nr<<'\n';
    for (int i=1;i<=n;i++)
    {
        if (l[i])
            g<<i<<' '<<l[i]<<'\n';
    }
    return 0;
}