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

struct Vertex
{
    int x;
    std::vector<int> myV;
    Vertex() : x(), myV() {}
    Vertex(int a) : x(a), myV() {}
};

void visitA(Vertex *A, int y, bool *bC, std::stack<int> &myS);
void visitB(Vertex *B, int y, bool *bC, std::vector<std::vector<int> > &strong, int nr);
void dfsA(Vertex *A, int nV, std::stack<int> &myS);
void dfsB(Vertex *B, int nV, std::stack<int> &myS, std::ostream& out);

int main()
{
    std::ifstream in("ctc.in");
    std::ofstream out("ctc.out");

    int nV, nE, a, b;

    in >> nV >> nE;

    Vertex *A = new Vertex[nV + 1], *B = new Vertex[nV + 1];

    for(int i = 1; i <= nV; i++)
        A[i] = Vertex(i), B[i] = Vertex(i);

    for(int i = 0; i < nE; i++)
    {
        in >> a >> b;
        A[a].myV.push_back(b);
        B[b].myV.push_back(a);
    }

    std::stack<int> myS;
    dfsA(A, nV, myS);
    dfsB(B, nV, myS, out);

    return 0;
}

void dfsB(Vertex *B, int nV, std::stack<int> &myS, std::ostream& out)
{
    int nr = 0, a;
    std::vector<std::vector<int> > strong;
    bool *bC = new bool[nV + 1];
    for(int i = 1; i <= nV; i++)
        bC[i] = false;
    while(!myS.empty())
    {
        a = myS.top();
        myS.pop();
        if(bC[a]) continue;
        strong.push_back(std::vector<int>());
        visitB(B, a, bC, strong, nr);
        nr++;
    }
    out << strong.size() << '\n';
    for(unsigned i = 0; i < strong.size(); i++)
    {
        for(unsigned j = 0; j < strong[i].size(); j++)
            out << strong[i][j] << ' ';
        out << '\n';
    }
}

void visitB(Vertex *B, int y, bool *bC, std::vector<std::vector<int> > &strong, int nr)
{
    bC[y] = true;
    for(unsigned i = 0; i < B[y].myV.size(); i++)
        if(!bC[B[y].myV[i]]) visitB(B, B[y].myV[i], bC, strong, nr);
    strong[nr].push_back(y);
}

void visitA(Vertex *A, int y, bool *bC, std::stack<int> &myS)
{
    bC[y] = true;
    for(unsigned i = 0; i < A[y].myV.size(); i++)
        if(!bC[A[y].myV[i]]) visitA(A, A[y].myV[i], bC, myS);
    myS.push(y);
}

void dfsA(Vertex *A, int nV, std::stack<int> &myS)
{
    bool *bC = new bool[nV + 1];
    for(int i = 1; i <= nV; i++)
        bC[i] = false;
    for(int i = 1; i <= nV; i++)
        if(!bC[i]) visitA(A, i, bC, myS);
}