#include<cstdio>
#include<string>
#include<vector>
#include<bitset>

using namespace std;

#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "cuplaj";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

typedef pair<int, int> PII;
const int NMAX = 10000 + 5;

int N, M, E;
vector<int> A[NMAX];
vector<int> B[NMAX];
int P[NMAX];
int Q[NMAX];
vector<PII> sol;
bitset<NMAX> viz;

int pair_up(int x) {
    if(viz[x])
        return 0;

    viz[x] = 1;

    for(auto y : A[x]) {
        if((!Q[y]) || (pair_up(Q[y]))) {
            P[x] = y;
            Q[y] = x;
            return 1;
        }
    }

    return 0;
}

int main() {
    int i, ok, x, y;

    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);

    scanf("%d%d%d", &N, &M, &E);

    while(E--) {
        scanf("%d%d", &x, &y);
        A[x].push_back(y);
        B[y].push_back(x);
    }

    do {
        ok = 0;
        viz = 0;

        for(i = 1; i <= N; i++)
            if(!P[i])
                ok |= pair_up(i);

    } while(ok);

    for(i = 1; i <= N; i++)
        if(P[i])
            sol.push_back(make_pair(i, P[i]));

    printf("%d\n", sol.size());

    for(auto p : sol)
        printf("%d %d\n", p.first, p.second);

    return 0;
}