#include<cstdio>
#include<cstring>
#include<vector>
#define NMAX 10010
using namespace std;
int dr[NMAX],st[NMAX],viz[NMAX],i,m,n,u,x,y,sol;
vector<int> v[NMAX];
int cupleaza(int i)
{
    if(viz[i]) return 0;
    viz[i]=1;
    for(vector<int>::iterator it=v[i].begin();it!=v[i].end();++it)
    {
        if(!dr[*it] || cupleaza(dr[*it]))
        {
            dr[*it]=i;
            st[i]=*it;
            return 1;
        }
    }
    return 0;
}

int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d",&n,&m,&u);
    int ok=1;
    for(;u;--u)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    while(ok)
    {
        ok=0;
        memset(viz,0,sizeof(viz));
        for(i=1;i<=n;++i)
        {
            if(!st[i]) ok|=cupleaza(i);
        }
    }
    for(i=1;i<=n;++i) if(st[i]) ++sol;
    printf("%d\n",sol);
    for(i=1;i<=n;++i)
        if(st[i]) printf("%d %d\n",i,st[i]);
    return 0;
}