#include <fstream>
#include <vector>
#include <cstring>

using namespace std;
ifstream in("cuplaj.in");
ofstream out("cuplaj.out");
int n,m,k,ok=1,st[10001],dr[10001],viz[10001],nr;
vector<int> v[10001];
int pairup(int x)
{
    if(viz[x])return 0;
    viz[x]=1;
    for(int i=0;i<v[x].size();i++)
    {
        int y=v[x][i];
        if(st[y]==0||pairup(st[y]))
        {
            st[y]=x;
            dr[x]=y;
            return 1;
        }
    }
    return 0;
}
int x,y;
int main()
{

    in>>n>>m>>k;
    for(int i=1;i<=k;i++)
    {
        in>>x>>y;
        v[x].push_back(y);
    }
    while(ok)
    {
        memset(viz,0,sizeof(viz));
        ok=0;
        for(int i=1;i<=n;i++)if(dr[i]==0&&pairup(i))ok=1;
    }
    for(int i=1;i<=n;i++)if(dr[i])nr++;
    out<<nr<<'\n';
    for(int i=1;i<=n;i++)if(dr[i])out<<i<<" "<<dr[i]<<'\n';
}