#include<bits/stdc++.h>
using namespace std;

const int maxN=(2e4)+5;

bool seen[maxN];
vector<int> v[maxN];
int r[maxN];
int l[maxN];
int x,y,n,m,e;

inline int path(int nod)
{
    if(seen[nod]) return 0;
    seen[nod]=1;
    for(auto it:v[nod])
    {
        if(!r[it])
        {
            r[it]=nod;
            l[nod]=it;
            return 1;
        }
    }

    for(auto it:v[nod])
    {
        if(path(r[it]))
        {
            r[it]=nod;
            l[nod]=it;
            return 1;
        }
    }
    return 0;
}
int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);

    scanf("%d%d%d",&n,&m,&e);
    for(int i=1;i<=e;i++)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(n+y);
    }

    int augment=1;
    while(augment)
    {
        augment=0;
        memset(seen,0,sizeof(seen));
        for(int i=1;i<=n;i++)
            if(!l[i]) augment|=path(i);
    }

    int cuplaj=0;

    for(int i=1;i<=n;i++)
        if(l[i]) cuplaj++;
    printf("%d\n",cuplaj);

    for(int i=1;i<=n;i++)
        if(l[i]) printf("%d %d\n",i,l[i]-n);

    return 0;
}