#include <cstdio>
#include <vector>
#include <bitset>
#include <stack>
#define NMAX 100009
using namespace std;

int N, M, order, found[NMAX], low[NMAX];
vector<int> G[NMAX];

stack<int> st;
bitset<NMAX> inStack;
vector< vector<int> > ctc;



void tarjan(const int& node) {
	found[ node ] = low[ node ] = ++order;

	st.push(node);
	inStack[ node ] = 1;

	for (auto it = G[node].begin(); it != G[node].end(); ++it) {
		if (!found[ *it ]) {
			tarjan(*it);
			// low[ node ] = min(low[ node ], low[ *it ]);
			if (low[ *it ] < low[ node ]) {
				low[ node ] = low[ *it ];
			}
		} else {
			// if (inStack[ *it ]) {
			// 	low[ node ] = min(low[ node ], found[ *it ]);
			// }
			if (inStack[ *it ] && found[ *it ] < low[ node ]) {
				low[ node ] = found[ *it ];
			}
		}
	}

	if (found[ node ] == low[ node ]) {
		int current;
		vector<int> tmp;
		ctc.push_back(tmp);

		while (!st.empty() && current != node) {
			ctc.back().push_back( current = st.top() );	
			st.pop();

			inStack[ current ] = 0;
		} 

		
	}
}

void ctcTarjan() {
	ctc.reserve(N);
	
	order = 0;
	for (int i = 1; i <= N; ++i) {
		if (!found[ i ]) {
			tarjan(i);
		}
	}
}

void printCTC() {
	printf("%d\n", (int) ctc.size());

	for (auto it = ctc.begin(); it != ctc.end(); ++it) {
		for (auto node = it->begin(); node != it->end(); ++node) {
			printf("%d ", *node);
		}
		printf("\n");
	}
}

void read() {
	scanf("%d%d", &N, &M);


	for (int i = 1; i <= M; ++i) {
		int x, y;
		scanf("%d%d", &x, &y);

		G[x].push_back(y);
	}
}




int main() {
	freopen("ctc.in", "r", stdin);
	freopen("ctc.out", "w", stdout);


	read();
	ctcTarjan();
	printCTC();


	return 0;
}