#include<cstdio>
#include<vector>
#include<cstring>
using namespace std;
const int N=10000;
vector<int>g[N+1];
int n1,n2,m;
int nxt[N+1];
int prc[N+1];
bool vis[N+1];
bool go(int dad){
    if(vis[dad])
        return false;
    vis[dad]=true;
    for(unsigned int i=0;i<g[dad].size();i++){
        int son=g[dad][i];
        if(!prc[son]){
            prc[son]=dad;
            nxt[dad]=son;
            return true;
        }
    }
    for(unsigned int i=0;i<g[dad].size();i++){
        int son=g[dad][i];
        if(prc[son]==dad)
            continue;
        if(go(prc[son])){
            prc[son]=dad;
            nxt[dad]=son;
            return true;
        }
    }
    return false;
}
int main(){
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d",&n1,&n2,&m);
    for(int i=1;i<=m;i++){
        int x,y;
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
    }
    bool f=true;
    while(f){
        f=false;
        memset(vis,0,sizeof(vis));
        for(int i=1;i<=n1;i++){
            if(!nxt[i])
                if(go(i))
                    f=true;
        }
    }
    int r=0;
    for(int i=1;i<=n1;i++)
        if(nxt[i])
            r++;
    printf("%d\n",r);
    for(int i=1;i<=n1;i++)
        if(nxt[i])
            printf("%d %d\n",i,nxt[i]);
    return 0;
}