#include <fstream>
#include <vector>
#include <bitset>
using namespace std;
ifstream cin("cuplaj.in");
ofstream cout("cuplaj.out");

#define nmax 10010

int n,m,e,x,y,match1[nmax],match2[nmax],ok,c;
vector<int> a[nmax];
bitset<nmax> v;

int match(int nod)
{
    vector<int>::iterator it;
    if (v.test(nod)==true) return 0;
    v.set(nod);
    for (it=a[nod].begin();it!=a[nod].end();it++)
        if (!match2[*it])
        {
            match1[nod]=*it;
            match2[*it]=nod;
            return 1;
        }
    for (it=a[nod].begin();it!=a[nod].end();it++)
        if (match(match2[*it]))
        {
            match1[nod]=*it;
            match2[*it]=nod;
            return 1;
        }
    return 0;
}

int main()
{
    int i,j;
    cin>>n>>m>>e;
    for (i=1;i<=e;i++)
    {
        cin>>x>>y;
        a[x].push_back(y);
    }
    ok=1;
    while(ok)
    {
        ok=0;
        v.reset();
        for (i=1;i<=n;i++)
            if (!match1[i])
                ok+=match(i);
    }
    for (i=1;i<=n;i++)
        if (match1[i]) c++;
    cout<<c<<'\n';
    for (i=1;i<=n;i++)
        if (match1[i])
            cout<<i<<" "<<match1[i]<<'\n';
}