#include<cstring>
#include<cstdio>
#include<vector>
using namespace std;
const int N=100000;
vector<int>g[N+1];
bool vis[N+1];
int father[N+1];
int l[N+1];
int res,n1,n2,m;
bool pairup(int dad){
    if(vis[dad])
        return 0;
    vis[dad]=true;
    for(int i=0;i<g[dad].size();i++){
        int son=g[dad][i];
        if(!father[son]){
            l[dad]=son;
            father[son]=dad;
            return 1;
        }
    }
    for(int i=0;i<g[dad].size();i++){
        int son=g[dad][i];
        if(pairup(son)){
            l[dad]=son;
            father[son]=dad;
            return 1;
        }
    }
    return 0;
}
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(!l[i])
                if(pairup(i))
                    f=true;
    }
    for(int i=1;i<=n1;i++)
        if(l[i]>0)
            res++;
    printf("%d\n",res);
    for(int i=1;i<=n1;i++)
        if(l[i]>0)
            printf("%d %d\n",i,l[i]);
    return 0;
}