#include <cstdio>
#include <cstring>

FILE* in=fopen("cuplaj.in","r");
FILE* out=fopen("cuplaj.out","w");

int a,b,n;

const int Q=100007;

int lst[Q],val[Q],nxt[Q],nr;

void add(int x, int y)
{
    val[++nr]=y;
    nxt[nr]=lst[x];
    lst[x]=nr;
}

bool viz[Q];

int next[Q],frm[Q];

bool adaos(int x)
{
    if(viz[x]==1)
        return 0;

    viz[x]=1;

    int p=lst[x];

    while(p)
    {
        if(frm[val[p]]==0)
        {
            frm[val[p]]=x;
            next[x]=val[p];
            return 1;
        }
        p=nxt[p];
    }

    p=lst[x];

    while(p)
    {
        if(adaos(frm[val[p]]))
        {
            frm[val[p]]=x;
            next[x]=val[p];
            return 1;
        }
        p=nxt[p];
    }
    return 0;
}


int main()
{

    fscanf(in,"%d%d%d",&a,&b,&n);

    int x,y;

    for(int i=1; i<=n; i++)
    {
        fscanf(in,"%d %d",&x,&y);
        add(x,y);
    }

    bool f=1;

    while(f)
    {
        f=0;
        memset(viz,0,sizeof viz);

        for(int i=1; i<=a; i++)
        {
            if(!next[i])
            {
                if(adaos(i))
                {
                    f=1;
                }
            }

        }
    }

    nr=0;

    for(int i=1; i<=a; i++)
    {
        if(next[i])
            nr++;
    }

    fprintf(out,"%d\n",nr);

    for(int i=1; i<=a; i++)
    {
        if(next[i])
        {
            fprintf(out,"%d %d\n",i,next[i]);
        }
    }


    return 0;
}