#include <fstream>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
int n, m, i, j, t, s, sol;
int x, y, numSCC;
int v[100001];
int f[100001], leader[100001];
vector <int> a[100001];
vector <int> b[100001];
bool exp[100001];
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

void DFS(int i)
{
    exp[i]=1;
    for (int cnt=0;cnt<b[i].size();cnt++) {
        if (exp[ b[i][cnt] ]==0) {
            DFS(b[i][cnt]);
        }
    }
    t++;
    f[i]=t;
}

void DFSSCC(int i)
{
    exp[i]=1;
    leader[i]=s;
    for (int cnt=0;cnt<a[i].size();cnt++) {
        if (exp[ a[i][cnt] ]==0) {
            DFSSCC(a[i][cnt]);
        }
    }
}



int main () {
    fin>>n>>m;
    for (i=1;i<=m;i++) {
        fin>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }

    t=0;

    for (i=n;i>=1;i--) {

        if (exp[i]==0) {

            DFS(i);

        }

    }



    for (i=1;i<=n;i++) {

        v[f[i]]=i;

    }



    memset(exp, 0, sizeof(exp));

    s=NULL;

    for (i=n;i>=1;i--) {

        if (exp[v[i]]==0) {

            s=v[i];

            DFSSCC(v[i]);

        }

    }



    memset (f, 0, sizeof(f));

    for (i=1;i<=n;i++) {

        if (f[leader[i]]==0)

            sol++;

        f[leader[i]]++;

    }



    for (i=1;i<=n;i++) {

        v[i]=i;

    }



    for (i=1;i<n;i++) {

        for (j=i;j<=n;j++) {

            if (leader[i]>leader[j]) {

                swap(leader[i], leader[j]);

                swap(v[i], v[j]);

            }

        }

    }



    fout<<sol<<"\n";

    for (i=1;i<=n;i++) {

        f[leader[i]]--;

        fout<<v[i]<<" ";

        if (f[leader[i]]==0)

            fout<<"\n";

    }

    /*

    fout<<f[n]<<","<<f[n-1]<<","<<f[n-2]<<","<<f[n-3]<<","<<f[n-4];

    for (i=1;i<=n;i++) {

        fout<<leader[i]<<" ";

    }*/

    return 0;

}