#include <bits/stdc++.h>
#include <fstream>
#include <stdio.h>

#include <ctype.h>
using namespace std;
ofstream fout("ctc.out");
const int NMAX = 100010;
vector<pair<int,bool>> graf[NMAX];
bool viz[NMAX];
bool vizPlus[NMAX],vizMinus[NMAX];
vector<vector<int>> comps;
class InParser {
private:
	FILE *fin;
	char *buff;
	int sp;
	char read_ch() {
		++sp;
		if (sp == 4096) {
			sp = 0;
			fread(buff, 1, 4096, fin);
		}
		return buff[sp];
	}
public:
	InParser(const char* nume) {
		fin = fopen(nume, "r");
		buff = new char[4096]();
		sp = 4095;
	}
	InParser& operator >> (int &n) {
		char c;
		while (!isdigit(c = read_ch()) && c != '-');
		int sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}
	InParser& operator >> (long long &n) {
		char c;
		n = 0;
		while (!isdigit(c = read_ch()) && c != '-');
		long long sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}
};
void dfsPlus(int node)
{
    for(int i = 0; i<graf[node].size(); i++)
    {
        if(!vizPlus[graf[node][i].first]&&graf[node][i].second&&!viz[graf[node][i].first])
        {
            vizPlus[graf[node][i].first] = true;
            dfsPlus(graf[node][i].first);
        }
    }
}
void dfsMinus(int node)
{
    for(int i = 0; i<graf[node].size(); i++)
    {
        if(!vizMinus[graf[node][i].first]&&!graf[node][i].second&&!viz[graf[node][i].first])
        {
            if(vizPlus[graf[node][i].first])
            {
                comps[comps.size()-1].push_back(graf[node][i].first);
                viz[graf[node][i].first] = true;
            }
            vizMinus[graf[node][i].first]=true;
            dfsMinus(graf[node][i].first);
        }
    }
}
void getComp(int node)
{
    fill(vizPlus,vizPlus+NMAX,false);
    fill(vizMinus,vizMinus+NMAX,false);
    viz[node]=true;
    vector<int> v;
    v.push_back(node);
    comps.push_back(v);
    vizPlus[node]=true;
    dfsPlus(node);
    vizMinus[node]=true;
    dfsMinus(node);
}
int main()
{

    ios::sync_with_stdio(0);
    InParser fin("ctc.in");
    int n,m;
    fin>>n>>m;
    for(int i = 0; i<m; i++)
    {
        int x,y;
        fin>>x>>y;
        graf[x].push_back({y,true});
        graf[y].push_back({x,false});
    }
    for(int i = 1; i<=n; i++)
    {
        if(!viz[i])
        {
            getComp(i);
        }
    }
    printf("%d\n",comps.size());
    for(int j = 0;j<comps.size();j++)
    {
        for(int i = 0;i<comps[j].size();i++)
            printf("%d ",comps[j][i]);
        printf("\n");
    }
    return 0;
}