#include <bits/stdc++.h>

#define nmax 100001

using namespace std;

vector<int> adj[nmax];
int l[nmax],r[nmax];
int ans;

bool visited[nmax];

bool cupl(int nod)
{
    if(visited[nod]) return 0;
    visited[nod]=1;


    for(int i=0;i<adj[nod].size();i++)
    {
        if(r[adj[nod][i]]==0)
        {
            l[nod]=adj[nod][i];
            r[adj[nod][i]]=nod;
            visited[nod]=0;
            return 1;
        }
    }

    for(int i=0;i<adj[nod].size();i++)
    {
        if(cupl(r[adj[nod][i]])==1)
        {
            l[nod]=adj[nod][i];
            r[adj[nod][i]]=nod;
            visited[nod]=0;
            return 1;
        }
    }
    visited[nod]=0;
    return 0;
}


int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);


    int nl,nr,m;
    cin>>nl>>nr>>m;
    for(int i=0;i<m;i++)
    {
        int a,b;
        cin>>a>>b;
        adj[a].push_back(b);
    }
    for(int i=1;i<=nl;i++)
    {
        if(cupl(i))
        {
            ans++;
        }
    }
    cout<<ans<<'\n';
    for(int i=1;i<=nl;i++)
    {
        if(l[i]!=0) cout<<i<<' '<<l[i]<<'\n';
    }
    return 0;
}