#include <bits/stdc++.h>
#define Nmax 1000
#define pb push_back

using namespace std;

int n,dr[Nmax],st[Nmax],viz[Nmax],cnt,v[Nmax][Nmax],l[Nmax];
vector <int> L[Nmax];

inline bool Cuplez(int nod)
{
    if(viz[nod]) return false;

    for(auto it : L[nod])
        if(!dr[it])
        {
            st[nod]=it; dr[it]=nod;
            return true;
        }

    viz[nod]=1;

    for(auto it : L[nod])
        if(Cuplez(dr[it]))
        {
            st[nod]=it; dr[it]=nod;
            viz[nod]=0; return true;
        }

    return false;
}

inline void Make_Lant(int nod)
{
    ++cnt;
    while(st[nod])
    {
        v[cnt][++l[cnt]]=nod;
        nod=st[nod]-n;
    }
    v[cnt][++l[cnt]]=nod;
}

int main()
{
    int m,x,y,i,j;
    ifstream cin("strazi.in");
    ofstream cout("strazi.out");
    cin>>n>>m;
    while(m--)
    {
        cin>>x>>y;
        L[x].pb(n+y);
    }
    int gata=0;
    while(!gata)
    {
        gata=1;
        for(i=1;i<=n;++i) viz[i]=0;
        for(i=1;i<=n;++i)
            if(!st[i] && Cuplez(i)) gata=0;
    }

    for(i=1;i<=n;++i)
        if(!dr[i+n]) Make_Lant(i);

    cout<<cnt-1<<"\n";
    for(i=1;i<cnt;++i) cout<<v[i][l[i]]<<" "<<v[i+1][1]<<"\n";
    for(i=1;i<=cnt;++i)
        for(j=1;j<=l[i];++j) cout<<v[i][j]<<" ";
    cout<<"\n";
    return 0;
}