#include <bits/stdc++.h>

std::vector< int > nd[100001];

std::vector< int > inv[100001];

int ord[100000];

int viz[100001];

std::vector< int > af[100000];

int q=0,c=0;

void dfs(int k){
    viz[k]=1;
    for(int i=0;i<nd[k].size();i++){
        if(viz[nd[k][i]]==0){
            dfs(nd[k][i]);
        }
    }
    ord[q]=k;
    q++;
}

void dfs1(int k){
    af[c].push_back(k);
    viz[k]=0;
    for(int i=0;i<inv[k].size();i++){
        if(viz[inv[k][i]]==1){
            dfs1(inv[k][i]);
        }
    }
}

int main()
{
    int n,m,a,b,i;
    FILE*fi,*fo;
    fi=fopen("ctc.in","r");
    fo=fopen("ctc.out","w");
    fscanf(fi,"%d%d",&n,&m);
    for(i=0;i<m;i++){
        fscanf(fi,"%d%d",&a,&b);
        nd[a].push_back(b);
        inv[b].push_back(a);
    }
    for(i=1;i<=n;i++){
        if(viz[i]==0)
            dfs(i);
    }
    for(i=n-1;i>=0;i--){
        if(viz[ord[i]]==1)
        {
            dfs1(ord[i]);
            c++;
        }
    }
    fprintf(fo,"%d\n",c);
    for(i=0;i<c;i++){
        for(int j=0;j<af[i].size();j++)
            fprintf(fo,"%d ",af[i][j]);
        fprintf(fo,"\n");
    }
    fclose(fi);
    fclose(fo);
    return 0;
}