#include <cstdio>
#include <vector>
#include <cstring>

using namespace std;

#define MAX_V1 10000
#define MAX_V2 10000

vector<int> L[MAX_V1]; // Lista de adyacencia de V1
int V1,V2,l[MAX_V1],r[MAX_V2];
bool visited[MAX_V1];

bool pairup(int u){
    if (visited[u])  return false;
    visited[u] = true;
    
    for(int i = L[u].size()-1;i>=0;--i){
        int v = L[u][i];
        
        if(r[v]==-1 || pairup(r[v])){
            l[u] = v;
            r[v] = u;
            return true;
        }
    }
    
    return false;
}

int hopcroft_karp(){
    bool change = true;
    memset(l,-1,sizeof(l));
    memset(r,-1,sizeof(r));
    
    while(change){
        change = false;
        memset(visited,false,sizeof(visited));
        
        for(int i = 0;i<V1;++i)
            if(l[i]==-1) change |= pairup(i);
    }
    
    int ret = 0;
    
    for(int i = 0;i<V1;++i)
        if(l[i]!=-1) ++ret;
    
    return ret;
}

int main(){
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);    
    
    int e,u,v;
    scanf("%d %d %d",&V1,&V2,&e);

    while(e--){
        scanf("%d %d",&u,&v);
        --u; --v;
        L[u].push_back(v);
    }
    
    printf("%d\n",hopcroft_karp());
    
    for(int i = 0;i<V1;++i)
        if(l[i]!=-1) printf("%d %d\n",1+i,1+l[i]);
    
    return 0;
}