#include <bits/stdc++.h>

using namespace std;
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
int n,m,e,ans,x,y;
int val[10005];
int tried[10005];
bool added[10005];
vector<int>nod[10005];
bool try_to_change(int pos,int when)
{
    if(tried[pos]==when)return false;
    tried[pos]=when;
    for(int i=0;i<nod[pos].size();i++)
        if(val[nod[pos][i]]==0)
        {
            val[nod[pos][i]]=pos;
            added[pos]=true;
            return true;
        }
    for(int i=0;i<nod[pos].size();i++)
        if(val[nod[pos][i]]!=pos && try_to_change(val[nod[pos][i]],when))
        {
            val[nod[pos][i]]=pos;
            added[pos]=true;
            return true;
        }
    return false;
}
int main()
{
    fin>>n>>m>>e;
    for(int i=1;i<=e;i++)
    {
        fin>>x>>y;
        nod[x].push_back(y);
    }
    for(int i=1;i<=n;i++)
        for(int j=0;j<nod[i].size() && !added[i];j++)
            if(val[nod[i][j]]==0)
            {
                val[nod[i][j]]=i;
                added[i]=true;
            }
    bool ok=true;
    int j=1;
    while(ok)
    {
        ok=false;
        for(int i=1;i<=n;i++)
            if(!added[i])
                ok|=try_to_change(i,j);
        j++;
    }
    for(int i=1;i<=m;i++)
        if(val[i]!=0)ans++;
    fout<<ans<<"\n";
    for(int i=1;i<=m;i++)
        if(val[i]!=0)
            fout<<val[i]<<" "<<i<<"\n";
    return 0;
}