#ifdef ONLINE_JUDGE
    #include <bits/stdc++.h>
#else
    #include <algorithm>
    #include <bitset>
    #include <cassert>
    #include <cmath>
    #include <cstdio>
    #include <cstdlib>
    #include <cstring>
    #include <iostream>
    #include <map>
    #include <set>
    #include <stack>
    #include <string>
    #include <utility>
    #include <vector>
    #include <queue>
    #include <climits>
#endif
 
using namespace std;
 
    // lambda : [] (int a, int b) -> bool { body return }
    // string r_str = R"(raw string)"
 
#define mp make_pair
#define mt make_tuple
#define eb emplace_back
#define pb push_back
#define LL long long
#define ULL unsigned long long
#define BASE 73
#define NMAX 10000
#define NMAX2 20001
#define MOD1 1000000007
#define ALL(V) (V).begin(), (V).end()
#define ALLR(V) (V).rbegin(), (V).rend()
#define CRLINE Duxar(__LINE__);
#define SHOWME(x) cerr << __LINE__ << ": " << #x << " = " << (x) << endl;
#define ENTER putchar('\n');
 
int dx4[] = {-1, 0, 1, 0};
int dy4[] = {0, 1, 0, -1};
 
int dx8[] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dy8[] = {0, 1, 1, 1, 0, -1, -1, -1};
 
void Duxar(int _this_line) {
#ifndef ONLINE_JUDGE
    printf("\n . . . . . . . . . . . . . Passed line - %d\n", _this_line);
#endif
}
 
template <class T>
void ReadNo(T &_value) {
    T _sign = 1;
    char ch;
    _value = 0;
    while(!isdigit(ch = getchar())) {
        (ch == '-') && (_sign = -1);
    }
    do {
        _value = _value * 10 + (ch - '0');
    } while(isdigit(ch = getchar()));
    _value *= _sign;
}
 
int N, M, E;
vector <vector <int> > graph;
vector <int> left_match, right_match;
vector <bool> visited;
 
bool SearchAugmented(int iam) {
    if (visited[iam]) {
        return false;
    }
    visited[iam] = true;
     
    for (auto to: graph[iam]) {
        if (right_match[to] == 0) {
            left_match[iam] = to;
            right_match[to] = iam;
            return true;
        }
    }
     
    for (auto to: graph[iam]) {
        if (SearchAugmented(right_match[to])) {
            left_match[iam] = to;
            right_match[to] = iam;
            return true;
        }
    }
     
    return false;
}
 
int main(){
    string file_input = "cuplaj";
#ifdef INFOARENA
    freopen((file_input + ".in").c_str(), "r", stdin);
    freopen((file_input + ".out").c_str(), "w", stdout);
#else
#ifndef ONLINE_JUDGE
    freopen("input.cpp", "r", stdin);
#endif
#endif
     
    int i, ans = 0, x, y;
    bool found;
    ReadNo(N); ReadNo(M); ReadNo(E);
    left_match.resize(N + 1);
    right_match.resize(M + 1);
    graph.resize(N + 1);
    visited.resize(N + 1);
     
    for (i = 0; i < E; ++i) {
        ReadNo(x); ReadNo(y);
        graph[x].pb(y);
    }
     
    found = true;
    while (found) {
        found = false;
        fill(ALL(visited), false);
        for (i = 1; i <= N; ++i) {
            if (left_match[i] == 0) {
                found = SearchAugmented(i) || found;
            }
        }
    }
     
    for (i = 1; i <= N; ++i) {
        ans += (left_match[i] != 0);
    }
     
    printf("%d\n", ans);
    for (i = 1; i <= N; ++i) {
        if (left_match[i]) {
            printf("%d %d\n", i, left_match[i]);
        }
    }
     
    return 0;
}