#include<fstream>
#include<cstring>
#include<vector>
#define N 10001
using namespace std;
ifstream F("cuplaj.in");
ofstream G("cuplaj.out");
vector<int> g[N];
int l[N],r[N],n,m,e,c=1,i,j;
bool u[N];
int P(int n)
{
    if(u[n])
		return 0;
    u[n]=1;
    int i,j=g[n].size();
    for(i=0;i<j;i++)
		if(!r[g[n][i]]) {
        	l[n]=g[n][i],r[g[n][i]]=n;
        	return 1;
    	}
    for(i=0;i<j;i++)
		if(P(r[g[n][i]])) {
        	l[n]=g[n][i],r[g[n][i]]=n;
        	return 1;
    	}
    return 0;
}
int main()
{
    F>>n>>m>>e;
    while(e--)
        F>>i>>j,g[i].push_back(j);
    while(c)
        for(c=0,memset(u,0,sizeof(u)),i=1;i<=n;++i)
			if(!l[i])
            	c|=P(i);
    for(j=0,i=1;i<=n;++i)
		j+=(l[i]>0);
    for(G<<j<<"\n",i=1;i<=n;++i)
		if(l[i]>0)
            G<<i<<" "<<l[i]<<"\n";
    return 0;
}