#include<cstdio>
#include<string>
#include<algorithm>
#include<vector>
#include<bitset>

using namespace std;

#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "ctc";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

const int NMAX = 100000 + 5;

int N, M, nr_ctc;
vector<int> V[NMAX];
vector<int> W[NMAX];
int P[NMAX], cnt;
vector<int> C[NMAX];
bitset<NMAX> viz;

void dfs(int x) {
    viz[x] = 1;
    for(auto y : V[x])
        if(!viz[y])
            dfs(y);
    P[++cnt] = x;
}

void dfst(int x) {
    viz[x] = 0;
    for(auto y : W[x])
        if(viz[y])
            dfst(y);
    C[nr_ctc].push_back(x);
}

int main() {
    int i, x, y;

    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);

    scanf("%d%d", &N, &M);

    while(M--) {
        scanf("%d%d", &x, &y);
        V[x].push_back(y);
        W[y].push_back(x);
    }

    for(i = 1; i <= N; i++)
        if(!viz[i])
            dfs(i);

    for(i = N; i >= 1; i--)
        if(viz[P[i]]) {
            nr_ctc++;
            dfst(P[i]);
        }

    printf("%d\n", nr_ctc);

    for(i = 1; i <= nr_ctc; i++) {
        for(auto x : C[i])
            printf("%d ", x);
        printf("\n");
    }

    return 0;
}