#include<cstdio>
#include<vector>
using namespace std;
vector<int>L[20100];
int n,m,q,i,j,a,b,nr,ok,l[20100],r[20100],v[20100];
FILE *f,*g;
int maxim(int a,int b){
    if(a>b)
        return a;
    return b;
}
int cupl(int nod){
    v[nod]=1;
    for(int i=0;i<L[nod].size();i++){
        int a=L[nod][i];
        if(r[a]==0){
            l[nod]=a;
            r[a]=nod;
            return 1;
        }
    }
    for(int i=0;i<L[nod].size();i++){
        int a=L[nod][i];
        if( v[ r[a] ] == 0 && cupl(r[a]) ){
            l[nod]=a;
            r[a]=nod;
            return 1;
        }
    }
    return 0;
}
int main(){
    f=fopen("cuplaj.in","r");
    g=fopen("cuplaj.out","w");
    fscanf(f,"%d%d%d",&n,&m,&q);
    for(i=1;i<=q;i++){
        fscanf(f,"%d%d",&a,&b);
        L[a].push_back(b);
    }
    m=maxim(m,n);
    while(1){
        ok=0;
        for(i=1;i<=m;i++){
            v[i]=0;
        }
        for(i=1;i<=n;i++){
            if(l[i]==0&&cupl(i)){
                nr++;
                ok=1;
                break;
            }
        }
        if(ok==0)
            break;
    }
    fprintf(g,"%d\n",nr);
    for(i=1;i<=n;i++){
        if(l[i]){
            fprintf(g,"%d %d\n",i,l[i]);
        }
    }
    fclose(f);
    fclose(g);
    return 0;
}