#include <iostream>
#include <fstream>
#include <vector>

#define vt vector
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()

using namespace std;

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

const int NMAX = 1e4;

int l[NMAX + 1];
int r[NMAX + 1];
bool viz[NMAX + 1];

vt <int> adj[NMAX + 1];

bool pairUp(int node){
    if(viz[node]){
        return 0;
    }
    viz[node] = 1;

    for(int vec : adj[node]){
        if(r[vec] == 0){
            l[node] = vec;
            r[vec] = node;
            return 1;
        }
    }

    for(int vec : adj[node]){
        if(pairUp(r[vec])){
            l[node] = vec;
            r[vec] = node;
            return 1;
        }
    }

    return 0;
}

void solve(){
    int n, m, e;
    fin >> n >> m >> e;

    for(int i = 1; i <= e; i++){
        int a, b;
        fin >> a >> b;
        adj[a].pb(b);
    }

    while(1){
        bool ok = 0;
        for(int i = 1; i <= n; i++){
            viz[i] = 0;
        }
        
        for(int i = 1; i <= n; i++){
            if(l[i] == 0){
                ok |= pairUp(i);
            }
        }

        if(!ok){
            break;
        }
    }

    int ans = 0;

    for(int i = 1; i <= n; i++){
        ans += (l[i] != 0);
    }

    fout << ans << '\n';
    for(int i = 1; i <= n; i++){
        if(l[i]){
            fout << i << ' ' << l[i] << '\n';
        }
    }
}

int main(){

    int T;
    // fin >> T;

    T = 1;

    while(T--){
        solve();
    }

    return 0;
}