//HighFlow
#include <cstdio>
#include <vector>
#include <string>
#include <bitset>
#include <stack>
#include <fstream>
#include <string.h>
#include <cmath>
#include <algorithm>
#define fcat(c) while (c!='\n') fscanf(f,"%c",&c)
#define cat(c) while (c!='\n') scanf("%c",&c)
#define For(i,st,dr,k) for (int i=st;i<=dr;i+=k)
#define ll (long long)
using namespace std;
FILE *f,*g;
int n,m;
vector <int> a[100100];
vector <vector <int> > sol;
stack<int> q;
int ind[100100],mn[100100];
int nv;
bool in_q[100100];


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

    f=fopen("ctc.in","r");
    g=fopen("ctc.out","w");

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

void df(int x)
{
    int i;
    ind[x]=mn[x]=++nv;
    q.push(x);
    in_q[x]=1;

    for (i=0;i<a[x].size();i++)
    {
        if (ind[a[x][i]]==0)
        {
            df(a[x][i]);
            mn[x]=min(mn[x],mn[a[x][i]]);
        }
        else
            if (in_q[a[x][i]])
                mn[x]=min(mn[x],mn[a[x][i]]);
    }
    if (ind[x]==mn[x])
    {
        vector <int> con;
        int y;

        do
        {
            y=q.top();q.pop();
            con.push_back(y);
            in_q[y]=0;
        }
        while (y!=x);

        sol.push_back(con);
    }

}

void solve()
{
    int i;

    for (i=1;i<=n;i++)
        if (ind[i]==0)
            df(i);
}

void write()
{
    int i,j;

    fprintf(g,"%d\n",sol.size());

    for (i=0;i<sol.size();i++,fprintf(g,"\n"))
        for (j=0;j<sol[i].size();j++)
            fprintf(g,"%d ",sol[i][j]);
}

int main()
{
    read();
    solve();
    write();
	return 0;
}