#include<cstdio>
#include<vector>

using namespace std;

const int nmax=100005;

vector<int>g[nmax],gt[nmax],r;
bool viz[nmax];
int st[nmax],top;
vector< vector<int> > sol;

inline void dfs1(int node)
{
    viz[node]=1;
    vector<int>::iterator it;
    for(it=g[node].begin();it!=g[node].end();++it)
        if(!viz[*it])
            dfs1(*it);
    st[++top]=node;
}

inline void dfs2(int node)
{
    vector<int>::iterator it;
    viz[node]=0;
    r.push_back(node);
    for(it=gt[node].begin();it!=gt[node].end();++it)
        if(viz[*it])
            dfs2(*it);
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    int n,i,j,m;
    scanf("%d%d",&n,&m);
    int x,y;
    for(i=1;i<=m;++i)
    {
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(i=1;i<=n;++i)
        if(!viz[i])
            dfs1(i);
    for(i=n;i;--i)
        if(viz[st[i]])
        {
            r.clear();
            dfs2(st[i]);
            sol.push_back(r);
        }
    printf("%d\n",sol.size());
    for(i=0;i<sol.size();++i)
    {
        for(j=0;j<sol[i].size();++j)
            printf("%d ",sol[i][j]);
        printf("\n");
    }
}