#include <bits/stdc++.h>

using namespace std;

ifstream f("cuplaj.in");
ofstream g("cuplaj.out");

bool pairup(int x){
    if(u[x])
        return 0;
    u[x] = 1;
    for(auto y:edges[x])
        if(r[y] == 0)
        {
            l[x] = y;
            r[y] = x;
            return 1;
        }
    for(auto y:edges[x])
        if(pairup(r[y]))
        {
            l[x] = y;
            r[y] = x;
            return 1;
        }
    return 0;
}

int main()
{
    f>>n>>m>>E;
    for(int i=1; i<=E; i++)
    {
        f>>x>>y;
        edges[x].push_back(y);
    }
    int change=1;
    while(change)
    {
        change=0;
        memset(u, 0, sizeof(u));
        for(int i=1; i<=n; i++)
            if(l[i]==0)
                change |= pairup(i);
    }
    int cuplaj=0;
    for(int i=1; i<=n; i++)
        if(l[i])
            cuplaj++;
    g<<cuplaj<<'\n';
    for(int i=1; i<=n; i++)
        if(l[i]>0)
            g<<i<<' '<<l[i]<<'\n';
    return 0;
}