#include<fstream>
#include<vector>'
#include<cstring>
#define nx 10007
using namespace std;
int n,m,nr,i,j,k,x,y,viz[nx],st[nx],dr[nx];
vector<int>v[nx];

ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");

int re(int x)
{
    if(viz[x])return 0;
    viz[x]=1;

    for(int j=0;j<v[x].size();j++)
    if(!dr[v[x][j]])
    {
        dr[v[x][j]]=x;
        st[x]=v[x][j];
        return 1;
    }

    for(int j=0;j<v[x].size();j++)
    if(re(dr[v[x][j]]))
    {
        dr[v[x][j]]=x;
        st[x]=v[x][j];
        return 1;
    }
    return 0;
}

int main()
{
    fin>>n>>m>>nr;
    for(i=1;i<=nr;i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
    }

    k=1;
    while(k)
    {
        memset(viz,0,sizeof(viz));
        k=0;
        for(i=1;i<=n;i++)if(!st[i])k+=re(i);
    }

    for(i=1;i<=n;i++)if(st[i])k++;
    fout<<k<<'\n';
    for(i=1;i<=n;i++)if(st[i])fout<<i<<' '<<st[i]<<'\n';
    return 0;
}