#include <bits/stdc++.h>
using namespace std;
vector<int>v[100005];
vector<int>g[100005];
int viz[100005];
int st[100005];
int cp;
void dfs(int nod)
{
    viz[nod]=1;
    int sz=v[nod].size();
    int i;
    for(i=0;i<sz;i++)
    {
        int p=v[nod][i];
        if(viz[p])continue;
        if(!viz[p])dfs(p);
    }
    st[cp--]=nod;
}
vector<int>sol[100005];
int cnt1=0;
int viz1[100005];
void dfs1(int nod)
{
    sol[cnt1].push_back(nod);
        viz1[nod]=1;
        int i;
    int sz=g[nod].size();
    for(i=0;i<sz;i++)
    {
        int p=g[nod][i];
        if(viz1[p])continue;
        if(!viz1[p])dfs1(p);
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    int m,n,x,y,i;
    scanf("%d%d",&m,&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
        g[y].push_back(x);
    }
    cp=m;
    for(i=1;i<=m;i++)
    {
        if(!viz[i])dfs(i);
    }
    cp=1;
    while(cp<=m)
    {
        if(!viz1[st[cp]])cnt1++,dfs1(st[cp]);
        cp++;
    }
    printf("%d\n",cnt1);
    for(i=1;i<=cnt1;i++)
    {
        int sz=sol[i].size();
        sort(sol[i].begin(),sol[i].end());
        for(int j=0;j<sz;j++)
        {
            printf("%d ",sol[i][j]);
        }
        printf("\n");
    }
    return 0;
}