#include <fstream>
#include <stack>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,k=1;
int viz[100011],low[100011],nr;

vector<int> L[100011],sol[10011];
stack<int> S;

void dfs(int nod){
    low[nod]=viz[nod]=k++;
    S.push(nod);
    for(unsigned register int i=0;i<L[nod].size();i++){
        if(!viz[L[nod][i]]){
            dfs(L[nod][i]);
        }
        if(low[nod]>low[L[nod][i]] && viz[L[nod][i]]>0){
            low[nod]=low[L[nod][i]];
        }
    }
    if(low[nod]==viz[nod]){
        nr++;
        while(S.top()!=nod){
            sol[nr].push_back(S.top());
            S.pop();
        }
        sol[nr].push_back(S.top());
        S.pop();
    }
}

int main(void){
    register int i,j,x,y;

    f>>n>>m;
    for(i=1;i<=m;i++){
        f>>x>>y;
        L[x].push_back(y);
    }

    for(i=1;i<=n;i++){
        if(!viz[i])
            dfs(i);
    }

    g<<nr<<"\n";
    for(i=1;i<=nr;i++){
        for(j=0;j<sol[i].size();j++)
            g<<sol[i][j]<<" ";
        g<<"\n";
    }
    return 0;
}