#include <bits/stdc++.h>
#define Nmax 100005
using namespace std;
int i, j, aux, n, m, x, y, k;
bool viz[Nmax], viz2[Nmax];
vector <int> comp[Nmax], g[Nmax], gt[Nmax];
stack <int> S;
void dfs(int x)
{
    viz[x] = true;
    for(int i = 0; i < g[x].size(); i ++)
    {
        int aux = g[x][i];
        if(viz[aux] == false)dfs(aux);
    }
    S.push(x);
}
void dfst(int x)
{
    viz2[x] = true;
    for(int i = 0; i < gt[x].size(); i ++)
    {
        int aux = gt[x][i];
        if(viz2[aux] == false)dfst(aux);
    }
}
int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    scanf("%d %d", &n, &m);
    for(i = 1; i <= m; i ++)
    {
        scanf("%d %d", &x, &y);
        g[x].push_back(y);
        gt[y].push_back(x);            //graful transpus
    }
    for(i = 1; i <= n; i ++)
        if(viz[i] == false)dfs(i);
    k = 1;
    while(!S.empty())
    {
        x = S.top();
        dfst(x);
        while(viz2[x] == true && !S.empty())
        {
            comp[k].push_back(x);
            S.pop();
            if(!S.empty())x = S.top();
        }
        k ++;
    }
    printf("%d\n", k - 1);
    for(i = 1; i < k; i ++)
    {
        for(j = 0; j < comp[i].size(); j ++)
            printf("%d ", comp[i][j]);
        printf("%s", "\n");
    }
    return 0;
}