#include <cstdio>
#include <vector>
#include <cstring>
#define NMAX 50005

using namespace std;

int n,m,i,j,x,y,nr,e;
vector<int>v[NMAX];
int L[NMAX],R[NMAX],viz[NMAX];

bool cupleaza(int nod)
{
    int i,fiu;
    viz[nod]=1;
    for(i=0;i<v[nod].size();++i)
    {
        fiu=v[nod][i];
        if(R[fiu] == 0)
        {
            R[fiu]=nod;
            L[nod]=fiu;
            return 1;
        }
    }
    for(i=0;i<v[nod].size();++i)
    {
        fiu=v[nod][i];
        if(viz[R[fiu]] == 0 && cupleaza(R[fiu]))
        {
            L[nod]=fiu;
            R[fiu]=nod;
            return 1;
        }
    }
    return 0;
}
int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d",&n,&m,&e);
    for(i=1;i<=e;++i)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    int ok=1;
    do
    {
        ok=1;
        memset(viz,0,sizeof(viz));
        for(i=1;i<=n;++i)
            if(L[i] == 0 && cupleaza(i)) ok=0;
    }while(ok == 0);
    for(i=1;i<=n;++i)
        if(L[i] != 0) ++nr;
    printf("%d\n",nr);
    for(i=1;i<=n;++i)
    {
        if(L[i] != 0) printf("%d %d\n",i,L[i]);
    }
    return 0;
}