#include <bits/stdc++.h>
#define maxn 1<<17
#define pb push_back
using namespace std;
vector<int> V[maxn],RS[maxn];
int N,M,T[maxn],P[maxn],rs,St[maxn],st;
void dfs(int x){
    St[++st] = x;
    for(auto y:V[x]) if(P[y]) P[x] = min(P[x],T[y]);
    else{
        int p=st;
        P[y] = T[y] = T[x] + 1;
        dfs(y);
        P[x] = min(P[x],P[y]);
        if(P[y] >= T[x]){
            RS[++rs].pb(x);
            while(p<st) RS[rs].pb(St[st--]);
        }
    }
}

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    ifstream cin("biconex.in");
    ofstream cout("biconex.out");
    cin >> N >> M;
    for(int x,y;M--;){
        cin >> x >> y;
        V[x].pb(y); V[y].pb(x);
    }
    T[1] = P[1] = 1;
    dfs(1);
    cout << rs << '\n';
    while(rs){
        for(auto it:RS[rs]) cout << it << ' ';
        cout << '\n'; rs--;
    }
}