#include <algorithm>
#include <cstdio>
#include <cmath>
#include <vector>
#include <queue>
#include <set>
#include <iomanip>
#include <stack>
#include <cstring>

#define NMax 100005
using namespace std;

vector<int> G[NMax];
vector<int> GT[NMax];
vector<int> c[NMax];
int viz[NMax],s[NMax];
int n,m,x,y,nr,comp;

void dfs(int nod){
    viz[nod] = 1;
    for(int i = 0; i < G[nod].size(); ++i){
        if(!viz[G[nod][i]])
            dfs(G[nod][i]);
    }
    s[++nr] = nod;
}
void dfsT(int nod){
    viz[nod] = 1;
    c[comp].push_back(nod);
    for(int i = 0; i < GT[nod].size(); ++i){
        if(!viz[GT[nod][i]])
            dfsT(GT[nod][i]);
    }
}
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i = 1; i <= m; ++i){
        scanf("%d%d",&x,&y);
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i = 1; i <= n; ++i)
        if(!viz[i])
            dfs(i);
    memset(viz,0,sizeof(viz));
    for(int i = nr; i >= 1; --i){
        if(viz[s[i]] == 0){
            comp++;
            dfsT(s[i]);
        }
    }
    printf("%d\n",comp);
    for(int i = 1; i <= comp; ++i){

        for(int j = 0; j < c[i].size(); ++j){
            printf("%d ",c[i][j]);
        }
        printf("\n");
    }
    return 0;
}