#include <algorithm>
#include <vector>
using namespace std;

#define pb push_back
#define DIM 260

int l[DIM],r[DIM],viz[DIM];
vector <int> g[DIM],d[DIM];
int n,m,nrt;

void read ()
{
    int i,x,y;

    scanf ("%d%d",&n,&m);
    for (i=1; i<=m; ++i)
    {
        scanf ("%d%d",&x,&y);
        g[x].pb (y);
    }
}

int pair_up (int nod)
{
    int i;

    if (viz[nod])
        return 0;
    viz[nod]=1;
    for (i=0; i<(int)g[nod].size (); ++i)
        if (!r[g[nod][i]])
        {
            r[g[nod][i]]=nod;
            l[nod]=g[nod][i];
            return 1;
        }
    for (i=0; i<(int)g[nod].size (); ++i)
        if (pair_up (r[g[nod][i]]))
        {
            l[nod]=g[nod][i];
            r[g[nod][i]]=nod;
            return 1;
        }
    return 0;
}

void solve ()
{
    int i,j,ok;

    do
    {
        ok=0;
        memset (viz,0,sizeof (viz));
        for (i=1; i<=n; ++i)
            if (!l[i] && pair_up (i))
                ok=1;
    }
    while (ok);
    for (i=1; i<=n; ++i)
        if (!r[i])
        {
            ++nrt;
            for (j=i; j; j=l[j])
                d[nrt].pb (j);
        }
    printf ("%d\n",nrt-1);
    for (i=1; i<nrt; ++i)
        printf ("%d %d\n",d[i].back (),d[i+1].front ());
    for (i=1; i<=nrt; ++i)
        for (j=0; j<(int)d[i].size (); ++j)
            printf ("%d ",d[i][j]);

}



int main ()
{
    freopen ("strazi.in","r",stdin);
    freopen ("strazi.out","w",stdout);

    read ();
    solve ();

    return 0;
}