#include <bits/stdc++.h>

using namespace std;

#define INFILE "cuplaj.in"
#define OUTFILE "cuplaj.out"

const int N_MAX = 1e5 + 5;

int n, m, edges;
bool visited[N_MAX];
int l[N_MAX], r[N_MAX];
vector<int> adj[N_MAX];

void connectNodes(int node1, int node2) {
    l[node1] = node2;
    r[node2] = node1;
}

bool link(int node){

    if(visited[node]) return false;
    visited[node] = true;

    for(auto &it : adj[node]){
        if(!r[it]){
            connectNodes(node, it);
            return true;
        }
    }

    for(auto &it : adj[node]){
        if(link(r[it])){
            connectNodes(node, it);
            return true;
        }
    }

    return false;

}

void solve(){

    cin >> n >> m >> edges;
    for(int i = 0; i < edges; ++i){
        int nodeLeft, nodeRight;
        cin >> nodeLeft >> nodeRight;
        adj[nodeLeft].push_back(nodeRight);
    }

    bool ok = true;
    do {
        ok = false;
        memset(visited, false, sizeof visited);
        for(int i = 1; i <= n; ++i){
            if(!l[i]) ok |= link(i);
        }
    }while(!ok);

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

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

}

int main(){
    ios_base::sync_with_stdio(false);
    freopen(INFILE, "r", stdin);
    freopen(OUTFILE, "w", stdout);
    cin.tie(0), cout.tie(0);
    solve();
    return 0;
}