#include<bits/stdc++.h>
using namespace std;
constexpr int N=100005;
struct Hopcroft_Karp
{
    int n,m;
    vector<int>g[N];
    int pa[N],pb[N];
    Hopcroft_Karp(){}
    Hopcroft_Karp(int _n,int _m):n(_n),m(_m){}
    void init(int _n,int _m)
    {
        n=_n,m=_m;
        for(int i=1;i<=n;i++)
            g[i].clear();
        return;
    }
    void add_edge(int u,int v)
    {
        g[u].push_back(v);
        return;
    }
    int dis[N];
    bool bfs()
    {
        queue<int>q;
        for(int u=1;u<=n;u++)
        {
            if(!pa[u])
            {
                dis[u]=0;
                q.push(u);
            }
            else dis[u]=-1;
        }
        bool found=false;
        while(!q.empty())
        {
            int u=q.front();
            q.pop();
            for(int v:g[u])
            {
                if(pb[v]&&dis[pb[v]]==-1)
                {
                    dis[pb[v]]=dis[u]+1;
                    q.push(pb[v]);
                }
                else if(!pb[v]) found=true;
            }
        }
        return found;
    }
    bool dfs(int u)
    {
        for(int v:g[u])
            if(!pb[v]||(dis[pb[v]]==dis[u]+1&&dfs(pb[v])))
            {
                pa[u]=v,pb[v]=u;
                return true;
            }
        dis[u]=-1;
        return false;
    }
    int max_matching()
    {
        fill(pa+1,pa+n+1,0);
        fill(pb+1,pb+m+1,0);
        int res=0;
        while(bfs())
        {
            for(int u=1;u<=n;u++)
                if(!pa[u]&&dfs(u)) res++;
        }
        return res;
    }
};
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr),cout.tie(nullptr);
    int n,m,e;
    cin>>n>>m>>e;
    Hopcroft_Karp solver(n,m);
    for(int i=1;i<=e;i++)
    {
        int u,v;
        cin>>u>>v;
        u++,v++;
        solver.add_edge(u,v);
    }
    int res=solver.max_matching();
    cout<<res<<"\n";
    for(int i=1;i<=n;i++)
        if(solver.pa[i]) cout<<i-1<<" "<<solver.pa[i]-1<<"\n";
    return 0;
}