#include <bits/stdc++.h>

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

using namespace std;
const int MAX = 1e5;

vector <int> g[2 * MAX + 1];
bool viz[2 * MAX + 1];
int p[2 * MAX + 1];

bool per(int nod){
    viz[nod] = true;
    for(int x: g[nod]){
        if(p[x] == 0){
            p[nod] = x;
            p[x] = nod;
            return true;
        }
        if(!viz[p[x]] && per(p[x])){
            p[nod] = x;
            p[x] = nod;
            return true;
        }
    }
    return false;
}



int main(){
    int n, m, e, a, b;

    in >> n >> m >> e;
    for(int i = 1; i <= e; i++){
        in >> a >> b;
        b += n;
        g[a].push_back(b);
        g[b].push_back(a);
    }

    int cnt = 0;
    bool ok;
    do{
        ok = false;
        for(int i = 1; i <= n; i++){
            if(!viz[i] && !p[i] && per(i)){
                cnt++;
                ok = true;
            }
        }
        for(int i = 1; i <= n + m; i++){
            viz[i] = false;
        }

    }while(ok);

    out << cnt << '\n';
    for(int i = 1; i <= n; i++){
        if(p[i]){
            out << i <<' '<< p[i] - n << '\n';
        }
    }
    return 0;
}