#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

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;
	}
} f("retele.in");

class OutParser {
private:
    FILE *fout;
    char *buff;
    int sp;

    void write_ch(char ch) {
        if (sp == 50000) {
            fwrite(buff, 1, 50000, fout);
            sp = 0;
            buff[sp++] = ch;
        } else {
            buff[sp++] = ch;
        }
    }


public:
    OutParser(const char* name) {
        fout = fopen(name, "w");
        buff = new char[50000]();
        sp = 0;
    }
    ~OutParser() {
        fwrite(buff, 1, sp, fout);
        fclose(fout);
    }

    OutParser& operator << (int vu32) {
        if (vu32 <= 9) {
            write_ch(vu32 + '0');
        } else {
            (*this) << (vu32 / 10);
            write_ch(vu32 % 10 + '0');
        }
        return *this;
    }

    OutParser& operator << (long long vu64) {
        if (vu64 <= 9) {
            write_ch(vu64 + '0');
        } else {
            (*this) << (vu64 / 10);
            write_ch(vu64 % 10 + '0');
        }
        return *this;
    }

    OutParser& operator << (char ch) {
        write_ch(ch);
        return *this;
    }
    OutParser& operator << (const char *ch) {
        while (*ch) {
            write_ch(*ch);
            ++ch;
        }
        return *this;
    }
} g("retele.out");

int n, m, viz1[50001], viz2[50001], cnt;

vector <int> a[50001], b[50001], ans[50001];

stack <int> q;

void dfs1(int nod)
{
    viz1[nod] = 1;

    for (auto it : a[nod]) {
        if (!viz1[it]) {
            dfs1(it);
        }
    }

    q.push(nod);
}

void dfs2(int nod)
{
    viz2[nod] = 1;

    for (auto it : b[nod]) {
        if (!viz2[it]) {
            dfs2(it);
        }
    }

    ans[cnt].push_back(nod);
}

int main()
{
    f >> n >> m;

    while (m--) {
        int x, y;

        f >> x >> y;

        a[x].push_back(y);
        b[y].push_back(x);
    }

    for (int i = 1; i <= n; ++i) {
        if (!viz1[i]) {
            dfs1(i);
        }
    }

    while (!q.empty()) {
        int nod = q.top();

        q.pop();

        if (!viz2[nod]) {
            cnt++;
            dfs2(nod);
        }
    }

    g << cnt << '\n';

    for (int i = 1; i <= cnt; ++i) {
        sort(ans[i].begin(), ans[i].end());
    }

    sort(ans + 1, ans + cnt + 1);

    for (int i = 1; i <= cnt; ++i) {
        g << (int) ans[i].size() << ' ';

        for (auto it : ans[i]) {
            g << it << ' ';
        }

        g << '\n';
    }

    return 0;
}