#include <cstdio>
#include <vector>
#include <cstring>
using namespace std;
vector<int>adiacenta[10001];
int st[10001],dr[10001];
bool fr[10001];
bool pairup(int nod)
{
    if(fr[nod])
        return 0;
    fr[nod] = 1;
    for(auto x:adiacenta[nod])
    {
        if(dr[x]==0)
        {
            st[nod] = x;
            dr[x] = nod;
            return 1;
        }
    }

    for(auto x:adiacenta[nod])
    {
        if(pairup(dr[x]))
        {
            st[nod] = x;
            dr[x] = nod;
            return 1;
        }
    }
    return 0;
}
int main()
{
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    int n,m,e;
    scanf("%d %d %d",&n,&m,&e);
    for(int i =1;i<=e;i++)
    {
        int x,y;
        scanf("%d %d %d",&x,&y);
        adiacenta[x].push_back(y);
    }

    int change = 1;
    while(change)
    {
        change = 0;
        memset(fr,0,sizeof(fr));
        for(int i = 1;i<=n;i++)
        {
            if(!st[i])
            {
                if(pairup(dr[i]))
                    change=1;
            }
        }
    }
    int cnt = 0;
    for(int i = 1;i<=n;i++)
    {
        cnt+=(st[i]>0);
    }
    printf("%d\n",cnt);
    for(int i = 1;i<=n;i++)
    {
        if(st[i])
            printf("%d %d\n",i,st[i]);
    }
}