#include <bits/stdc++.h>
#define ll long long
#define enl putchar('\n')
#define all(x) (x).begin(),(x).end()
#define debug(x) printf(" "#x":%d\n",x);
using namespace std;
const int MAXN = 2e5 + 5;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 998244353;
typedef pair<int, int> pii;
char buf[1 << 21], * p1 = buf, * p2 = buf, obuf[1 << 21], * o = obuf, of[35];
#define gc()(p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
inline ll qpow(ll a, ll n) { ll res = 1; while (n) { if (n & 1)res = res * a % mod; n >>= 1; a = a * a % mod; }return res; }
template <class T = int>inline T read() { T s = 0, f = 1; char c = gc(); for (; !isdigit(c); c = gc())if (c == '-')f = -1; for (; isdigit(c); c = gc())s = s * 10 + c - '0'; return s * f; }
inline void read(int* a, int n) { for (int i = 1; i <= n; ++i)a[i] = read(); }
inline int inal(char* s) { int n = 0; for (s[0] = gc(); !isalpha(s[0]); s[0] = gc()); for (; isalpha(s[n]); s[++n] = gc()); return s[n] = 0, n; }
inline int indi(char* s) { int n = 0; for (s[0] = gc(); !isdigit(s[0]); s[0] = gc()); for (; isdigit(s[n]); s[++n] = gc()); return s[n] = 0, n; }
inline void outd(auto* a, int n) { for (int i = 1; i <= n; ++i)printf("%d ", a[i]); enl; }
int n, m, q;
int L, R;

vector<int>E[MAXN];
int px[MAXN], py[MAXN];
int pre[MAXN], vis[MAXN], TC;
void aug(int x) {
    while (x) {
        int tmp = px[pre[x]];
        px[pre[x]] = x;
        py[x] = pre[x];
        x = tmp;
    }
}
bool bfs(int x) {
    vector<int>vec;
    queue<int>que;
    que.push(x);
    while (!que.empty()) {
        int u = que.front();
        que.pop();
        for (int v : E[x]) {
            if (vis[v] == TC)continue;
            vis[v] = TC;
            pre[v] = u;
            vec.push_back(v);
            if (!py[v]) {
                aug(v);
                for (auto x : vec) pre[x] = 0;
                return 1;
            } else {
                que.push(py[v]);
            }
        }
    }
    for (auto x : vec) pre[x] = 0;
    return 0;
}
random_device rd;
void solve() {
    L = read(), R = read(), m = read();
    for (int i = 1; i <= m; ++i) {
        int u = read() + 1, v = read() + 1;
        E[u].push_back(v);
    }
    for (int i = 1; i <= L; ++i) {
        shuffle(E[i].begin(), E[i].end(), rd);
    }
    int ans = 0;
    for (int i = 1; i <= L; i++) {
        ++TC;
        ans += bfs(i);
    }
    printf("%d\n", ans);
    for (int i = 1; i <= L; ++i)
        if (px[i])printf("%d %d\n", i - 1, px[i] - 1);
}
signed main(signed argc, char const* argv[]) {
    clock_t c1 = clock();
#ifdef LOCAL
    freopen("in.in", "r", stdin);
    freopen("out.out", "w", stdout);
#endif
    //=============================================================
    int TxT = 1;
    // TxT = read();
    while (TxT--)
        solve();
    //=============================================================
#ifdef LOCAL
    end :
    cerr << "Time Used:" << clock() - c1 << "ms" << endl;
#endif
    return 0;
}