#include <bits/stdc++.h>

using namespace std;

vector <int> v[10555];

int f[10555];

int l[10555],r[10555];

int el;

bool dfs(int k)
{
    for(auto a:v[k])
    {
        if(f[a]!=el)
        {
            f[a]=el;
            if(r[a]==0 || dfs(r[a]))
            {
                l[k]=a;
                r[a]=k;
                return true;
            }
        }
    }
    return false;
}

int main()
{
    ifstream cin("cuplaj.in");
    ofstream cout("cuplaj.out");
    int n,m,k,x,y;
    cin>>n>>m>>k;
    for(int i=1;i<=k;++i)
    {
        cin>>x>>y;
        v[x].push_back(y);

    }
    int cnt=0;
    for(int i=1;i<=n;++i)
    {
        el=i;
        if(l[i]==0 && dfs(i))
        {
            ++cnt;
        }
    }
    cout<<cnt<<"\n";
    for(int i=1;i<=n;++i)
    {
        if(l[i])
        {
            cout<<i<<" "<<l[i]<<"\n";
        }
    }
    return 0;
}