#include<iostream>
#include<vector>
#include<cstring>
#include<queue>

using namespace std;
const int maxm = 1e6+5;
const int maxn = 3e5+5;
int edge[maxm], ver[maxm], nxt[maxm], head[maxn];
int now[maxn];
int cnt = 1;
void add(int x, int y, int z){
	edge[++cnt] = z, ver[cnt] = y, nxt[cnt] = head[x], head[x] = cnt;
}
int d[maxn];
int l,r,m,s,t;

bool bfs(){
	queue<int> q;
	memset(d,0,sizeof d);
	q.push(s);
	d[s] = 1;
	while(!q.empty()){
		int f = q.front();
		q.pop();
		for (int i = head[f]; i; i = nxt[i]){
			int to = ver[i];
			if (edge[i] && !d[to]){
				q.push(to);
				d[to] = d[f]+1;
				if (to == t) return 1;
			}
		}
	}
	return 0;
}
int dinic(int x, int flow){
	if (x == t) return flow;
	int rst = flow;
	for (int i = head[x]; i && rst; i = nxt[i]){
		now[x] = i;
		int y = ver[i], z = edge[i];
		if (edge[i] && d[y] == d[x]+1){
			int to = dinic(y,min(rst,z));
			if (!to) d[y] = 0;
			rst -= to;
			edge[i] -= to;
			edge[i^1] += to;
		}
		
	}
	return flow-rst;
}



signed main(){
	// freopen("a.in","r",stdin);

    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    cin >> l >> r >> m;
    for (int i = 1; i <= m; i++){
        int x,y;
        cin >> x >> y;
        x++,y++;
        add(x,y+l,1);
        add(y+l,x,0);
    }
    s = 0, t = l+r+1;
    for (int i = 1; i <= l; i++) add(s,i,1), add(i,s,0);
    for (int i = l+1; i <= l+r; i++) add(i,t,1), add(t,i,0);

    int maxflow = 0;
    while(bfs()) maxflow += dinic(s,1e9);
    
    cout << maxflow << endl;
    for (int i = 1; i <= l; i++){
        for (int j = head[i]; j; j = nxt[j]){
            if (ver[j] > l && !edge[j]){
                cout << i-1 << " " << ver[j]-l-1 << ' ';
            }
        }
    }

	return 0;
}