#include <stdio.h>
#include <vector>
#define NMax 260

int n, m, uz[NMax], path[NMax], mat[NMax][NMax];
std::vector<int> a[NMax], fin;

void citire();
void rez();
void bfs( int x );
void redo( int x, int type );
void redo2( int x, int type );
void afis( int x, FILE *g );

int main()
{
	citire();
	rez();
	return 0;
}
void afis( int x, FILE *g )
{
	if ( path[x] == -1 )
	{
		fprintf( g, "%d ", x );
		return;
	}
	afis( path[x], g );
	fprintf( g, "%d ", x );
}
void redo2( int x, int type )
{
	if ( path[x] == -1 )
		return;

	uz[x] = type;
	redo( path[x], type-1 );
}
void redo( int x, int type )
{
	if ( path[x] == -1 )
		return;

	uz[x] = type;
	redo( path[x], type );
}
void bfs( int x )
{
	int i, in, sf, max, nrmax, first, ok, okbig = 0, C[NMax];
	std::vector<int> lista;

	in      = sf = 0;
	C[0]    = x;
	path[x] = -1;
	uz[x]   = 1;
	nrmax   = x;

	while( in <= sf )
	{
		first = C[in++];
		max = a[first].size();

		// vad vecinii unui nod
		for (i=0,ok=0; i<max; i++)
		{
			if ( !uz[a[first].at(i)] )
			{
				ok = okbig = 1;
				C[++sf] = a[first].at(i);
				uz[C[sf]] = 1 + uz[first];
				path[C[sf]] = first;
			}
			else
			{
				path[a[first].at(i)] = first;
				okbig = 2;
			}
		}	
		// daca nu ma mai pot duce nicaieri
		if ( !ok )
		{
			// il adaug in lista
			lista.push_back( first );
			// vad daca am un vf mai bun ca lungime
			if ( uz[nrmax] < uz[first] )
				nrmax = first;
		}
	}
	
	max = lista.size();
	for (i=0; i<max; i++)
		if ( lista.at(i) != nrmax )
			redo( lista.at(i), 0 );
	redo2( nrmax, uz[nrmax] );

	if ( okbig == 0 )
	{
		okbig = 1;
		for (i=1; i<=n && okbig; i++)
		{
			if ( mat[i][x] && !uz[i] )
				okbig = 0;
		}
		if ( okbig )
			fin.push_back( x );
	}
	else if ( okbig == 1 )
	{
		fin.push_back( nrmax );
	}

}
void rez()
{
	int i, max;
	FILE *g = fopen( "strazi.out", "wt" );


	for (i=1; i<=n; i++)
		if ( !uz[i] )
		{
			bfs( i );
		}

	max = fin.size();
	fprintf( g, "%d\n", max-1 );
	for (i=0; i<max-1; i++)
	{
		fprintf( g, "%d %d\n", fin[i], fin[i+1] );
		path[fin[i+1]] = fin[i];
	}
	afis( fin[i], g );
}
void citire()
{
	int i, x, y;
	FILE *f = fopen( "strazi.in", "rt" );	

	fscanf( f, "%d %d", &n, &m );
	for (i=0; i<m; i++)
	{
		fscanf( f, "%d %d", &x, &y );
		a[x].push_back( y );
		mat[x][y] = 1;
	}

	fclose( f );
}