#include <bits/stdc++.h>
#include <cstring>
#pragma GCC optimize ("O3")
#define din cin
#define dout out
#define pi 3.14159265359
#define sw(x,y) x^=y,y^=x,x^=y
#define bmin(a,b)((a<b)?(a):(b))
#define bmax(a,b)((a>b)?(a):(b))
#define bminify(a,b)a=bmin(a,b)
#define bmaxify(a,b)a=bmax(a,b)
#define forq(i,ii,n)for(i=ii;i<n;i++)
#define f first
#define s second
#define mod 1000000297ll
#define nmax 100001
using namespace std;
typedef long long ll;
//ifstream in("fmcm.in");
//ofstream out("fmcm.out");
FILE *fin=fopen("ctc.in","r");
FILE *fout=fopen("ctc.out","w");
int n,m,i,j,k,l,z,c[nmax],p[nmax],s[nmax];bitset<nmax>b;
vector<int>g[nmax];char r[1000000],*rp=r+9;
void tj(int v)
{
    p[v]=s[v]=++z,b[v]=1,c[l++]=v;
    for(auto i:g[v])
        if(p[i])
            {if(b[i])
                bminify(s[v],p[i]);}
            else tj(i),bminify(s[v],s[i]);
    if(s[v]==p[v])
    {
        ++k,rp+=sprintf(rp,"\n");
        do{b[c[--l]]=0,rp+=sprintf(rp,"%d ",c[l]);}while(c[l]!=v);
    }
}
int main()
{
fscanf(fin,"%d%d",&n,&m);
for(k=0;k<m;k++)fscanf(fin,"%d%d",&i,&j),g[i].emplace_back(j);
k=0;
for(i=1;i<=n;i++)
    if(p[i]==0)
        tj(i);
fprintf(fout,"%d%s",k,r+9);
}