#include<cstdio>
#include<cstdlib>
#include<vector>

using namespace std;

vector<short int>v[10001];
short int a[10001],b[10001];
char atins[10001];
int n,m,x,y,p,i;

int cuplaj(short int x)
{
    short int lim=v[x].size(),i;
    if(atins[x]) return 0;
    atins[x]=1;
    for(i=0;i<lim;i++)
    {
        if(b[v[x][i]]==0)
        {
            a[x]=v[x][i];
            b[v[x][i]]=x;
            return 1;
        }
    }
    for(i=0;i<lim;i++)
    {
        if(cuplaj(b[v[x][i]]))
        {
            a[x]=v[x][i];
            b[v[x][i]]=x;
            return 1;
        }
    }
    return 0;
}

int main()
{
    freopen("cuplaj.in", "r", stdin);
    freopen("cuplaj.out", "w", stdout);
    scanf("%d%d%d",&n,&m,&p);
    for(i=1;i<=p;i++)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    p=1;
    while(p)
    {
        p=0;
        for(i=1;i<=n;i++) atins[i]=0;
        for(i=1;i<=n;i++)
        {
            if(a[i]==0&&cuplaj(i)) p=1;
        }
    }
    x=0;
    for(i=1;i<=n;i++) if(a[i]) x++;
    printf("%d\n",x);
    for(i=1;i<=n;i++) if(a[i]) printf("%d %d\n",i,a[i]);
    fclose(stdin);
    fclose(stdout);
    return 0;
}