#include <cstdio>
#include <random>
#include <ctime>
#include <vector>
#include <algorithm>
#define rep(i, d, u) for(int i = d; i <= u; ++i)
#define gep(i, a) for(int i = firs[a]; i; i = neig[i])
#define tep(i, a) for(int i = tfir[a]; i; i = tnei[i])
int ured() {
	int re = 0;
	char ch;
	do {
		ch = getchar();
	} while('9' < ch || ch < '0');
	do {
		re = re * 10 + (ch ^ '0');
	} while('0' <= (ch = getchar()) && ch <= '9');
	return re;
}
void uwit(int da) {
	int ch[21], cn = 0;
	do {
		ch[++cn] = da - da / 10 * 10;
	} while(da /= 10);
	do {
		putchar('0' ^ ch[cn]);
	} while(--cn);
}
std :: mt19937 tran(time(0) * 1000 + clock());
typedef unsigned long long ull;
const int _maxn = 200011;
int n, m, a, b, firs[_maxn], neig[_maxn << 1], arri[_maxn << 1], cnts[_maxn], fath[_maxn];
int tfir[_maxn], tnei[_maxn << 1], tarr[_maxn << 1], dept[_maxn << 1], coum;
bool inta[_maxn], visi[_maxn];
ull valu[_maxn];
std :: vector<int> dats;
std :: vector<std :: vector<int>> rans;
void dfs1(int at, int fa) {
	visi[at] = inta[at] = 1, dats . push_back(at);
	gep(i, at) {
		if(i != fa) {
			if(inta[arri[i]]) {
				ull rg = 0ull + tran() << 32 | tran();
				valu[at] ^= rg, valu[arri[i]] ^= rg, ++cnts[at], --cnts[arri[i]];
			} else if(!visi[arri[i]]) {
				fath[arri[i]] = at, dept[arri[i]] = dept[at] + 1, dfs1(arri[i], i ^ 1), valu[at] ^= valu[arri[i]], cnts[at] += cnts[arri[i]];
			}
		}
	}
	inta[at] = 0;
}
void adde(int le, int ri) {
	tnei[++coum << 1] = tfir[le], tfir[le] = coum << 1, tarr[coum << 1] = ri;
	tnei[coum << 1 | 1] = tfir[ri], tfir[ri] = coum << 1 | 1, tarr[coum << 1 | 1] = le;
}
void dfs2(int at) {
	visi[at] = 1, dats . push_back(at);
	tep(i, at) {
		if(!visi[tarr[i]]) {
			dfs2(tarr[i]);
		}
	}
}
int main() {
	n = ured(), m = ured();
	rep(i, 1, m) {
		a = ured(), b = ured(), neig[i << 1] = firs[a], firs[a] = i << 1, arri[i << 1] = b;
		neig[i << 1 | 1] = firs[b], firs[b] = i << 1 | 1, arri[i << 1 | 1] = a;
	}
	rep(i, 0, n - 1) {
		if(!visi[i]) {
			dats . clear(), dfs1(i, 0), std :: sort(dats . begin(), dats . end(), [](int le, int ri) {
				return valu[le] == valu[ri] ? dept[le] < dept[ri] : valu[le] < valu[ri];
			});
			for(int j = 0, k; j < dats . size(); j = k) {
				for(k = j + 1; k < dats . size() && valu[dats[k]] == valu[dats[j]]; ++k);
				if(cnts[dats[k - 1]] > 1) {
					adde(fath[dats[j]], dats[k - 1]);
				}
			}
		}
	}
	rep(i, 0, n - 1) {
		visi[i] = 0;
	}
	rep(i, 0, n - 1) {
		if(!visi[i]) {
			dats . clear(), dfs2(i), rans . push_back(dats);
		}
	}
	uwit(rans . size()), putchar('\n');
	for(std :: vector<int> &i : rans) {
		uwit(i . size());
		for(int j : i) {
			putchar(' '), uwit(j);
		}
		putchar('\n');
	}
	return 0;
}