#include <cstdio>
#include <vector>

#define NMax 100005
using namespace std;

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

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] = 0;
    for(int i = 0; i < GT[nod].size(); ++i)
        if(viz[GT[nod][i]])
            dfst(GT[nod][i]);
    cc[cl].push_back(nod);
}
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);
    for(int i = n; i >= 1; --i){
        if(viz[s[i]]){
            cl++;
            dfst(s[i]);
        }
    }
    printf("%d\n",cl);
    for(int i = 1; i <= cl; ++i){

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