# include <fstream>
# include <vector>
# include <algorithm>
# include <cstring>

# define MAXN  10005

using namespace std;

ifstream f("cuplaj.in");
ofstream g("cuplaj.out");


vector <int> G[ MAXN ];

int l[ MAXN ], r[ MAXN ], u[ MAXN ];


int pairup( const int n )
{
	int i;
    if ( u[ n ] )  
		return 0;
    u[ n ] = 1;
   
	for ( i = 0 ; i < G[ n ].size() ; i++ )
		if ( r[ G[ n ][ i ] ] == 0 )	
		{
			l[ n ] = G[ n ][ i ];
		    r[ G[ n ][ i ] ] = n;
	     	return 1;
		}
    
	for ( i = 0 ; i < G[ n ].size() ; i++ )
		if ( pairup( r[ G[ n ][ i ] ] ) == 1  )	
		{
			l[ n ] = G[ n ][ i ];
		    r[ G[ n ][ i ] ] = n;
		    return 1;
		}
		
		return 0;
}

int main(void)
{
    int n, m, cnt_edges, i, change;
	
	f >> n >> m >> cnt_edges;
	
	for ( i = 1 ; i <= cnt_edges ; i++ )
    {
        int x, y;
		f >> x >> y;
        G[ x ].push_back( y );
    }
	change = 1;
	while( change )
    {
        change = 0;
        memset( u, 0, sizeof( u ) );
      
        for ( i = 1 ; i <= n ; i++ )		
			if ( !l[ i ] )
				if ( pairup( i ) )
					change = 1;
    }
    int cuplaj = 0;
  
    for ( i = 1 ; i <= n ; i++ )
		if ( l[ i ] > 0 )
	cuplaj = cuplaj +  1;
	
  
	g << cuplaj << "\n";

	for ( i = 1 ; i <= n ; i++ )
	if (l[ i ] > 0)
		g << i << " " << l[ i ] <<"\n";

    return 0;
}