// what is matter? never mind. 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2") 
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
#define int long long
#define ull unsigned long long
#define SZ(x) ((int)((x).size()))
#define ALL(x) (x).begin(),(x).end()
using namespace std;
inline int read()
{
    char c=getchar();int x=0;bool f=0;
    for(;!isdigit(c);c=getchar())f^=!(c^45);
    for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
    if(f)x=-x;return x;
}

#define mod 998244353
struct modint{
	int x;
	modint(int o=0){x=o;}
	modint &operator = (int o){return x=o,*this;}
	modint &operator +=(modint o){return x=x+o.x>=mod?x+o.x-mod:x+o.x,*this;}
	modint &operator -=(modint o){return x=x-o.x<0?x-o.x+mod:x-o.x,*this;}
	modint &operator *=(modint o){return x=1ll*x*o.x%mod,*this;}
	modint &operator ^=(int b){
		modint a=*this,c=1;
		for(;b;b>>=1,a*=a)if(b&1)c*=a;
		return x=c.x,*this;
	}
	modint &operator /=(modint o){return *this *=o^=mod-2;}
	friend modint operator +(modint a,modint b){return a+=b;}
	friend modint operator -(modint a,modint b){return a-=b;}
	friend modint operator *(modint a,modint b){return a*=b;}
	friend modint operator /(modint a,modint b){return a/=b;}
	friend modint operator ^(modint a,int b){return a^=b;}
	friend bool operator ==(modint a,modint b){return a.x==b.x;}
	friend bool operator !=(modint a,modint b){return a.x!=b.x;}
	bool operator ! () {return !x;}
	modint operator - () {return x?mod-x:0;}
	bool operator <(const modint&b)const{return x<b.x;}
};
inline modint qpow(modint x,int y){return x^y;}

vector<modint> fac,ifac,iv;
inline void initC(int n)
{
	if(iv.empty())fac=ifac=iv=vector<modint>(2,1);
	int m=iv.size(); ++n;
	if(m>=n)return;
	iv.resize(n),fac.resize(n),ifac.resize(n);
	For(i,m,n-1){
		iv[i]=iv[mod%i]*(mod-mod/i);
		fac[i]=fac[i-1]*i,ifac[i]=ifac[i-1]*iv[i];
	}
}
inline modint C(int n,int m){
	if(m<0||n<m)return 0;
	return initC(n),fac[n]*ifac[m]*ifac[n-m];
}
inline modint sign(int n){return (n&1)?(mod-1):(1);}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 200006
#define inf 0x3f3f3f3f

int n,m,rt;
int e[105][105],deg[105];
vi g[105];

int fa[105],dep[105];
vi son[105];
vi que;

bool del[105];

void dfs(int u,int pa){
	que.pb(u);
	fa[u]=pa,dep[u]=dep[pa]+1;
	for(int v:g[u])
		if(v!=pa && !dep[v]) son[u].pb(v),dfs(v,u);
}
int col[maxn];

void chain(vi o){
	cout<<n*2<<"\n";
	For(i,1,n*2){
		For(j,0,n-1) {
			if((j&1)==(i&1) && j) col[o[j]]=o[j-1];
			else col[o[j]]=o[j];
		}
		For(u,1,n) cout<<col[u]<<" "; cout<<"\n";
	}
	exit(0);
}

void out(int rt,int dw){
	cout<<n*2<<"\n";
	For(t,1,n*2){
		For(i,1,n){
			if(i==rt) {
				if(t&1) cout<<dw<<" ";
				else cout<<rt<<" ";
			}else{
				if((t&1)==(dep[i]&1)) cout<<fa[i]<<" ";
				else cout<<i<<" ";
			}
		}
		cout<<"\n";
	}
	exit(0);
}

void dfs2(int u,int pa){
//	cout<<"Dfs2 "<<u<<" "<<pa<<" "<<dep[pa]<<"\n";
	fa[u]=pa,dep[u]=dep[pa]+1;
	for(int v:g[u])
		if(v!=pa && !dep[v] && !del[v]) dfs2(v,u);
}

vi g2[105];
void dfsc(int u,int pa){
	que.pb(u);
	for(int v:g2[u]) if(v!=pa) dfsc(v,u);
}

signed main()
{
	n=read(),m=read();
	
	For(i,1,m){
		int u=read(),v=read();
		++u,++v;
		e[u][v]=e[v][u]=1;
		++deg[u],++deg[v];
		g[u].pb(v),g[v].pb(u);
	}
	
	dfs(1,0);
	
	bool ok1=1;
	For(i,1,n)
		for(int v:son[i]) g2[i].pb(v),g2[v].pb(i);
	For(i,1,n) ok1&=(g2[i].size()<=2);
	if(ok1){
		int u=1;
		For(i,1,n) if(g2[i].size()==1) u=i;
		que.clear();
		dfsc(u,0);
		chain(que);
		exit(0);
	}
	
	int u=0;
	For(i,1,n) if(son[i].size()>1 && dep[i]>=dep[u]) u=i;
	int f=fa[u];
	if(!f){
		For(i,1,n) son[i].clear(),fa[i]=dep[i]=0; que.clear();
		int v=son[u][0];
		dfs(v,0);
		u=0;
		For(i,1,n) if(son[i].size()>1 && dep[i]>=dep[u]) u=i;
		f=fa[u];
		assert(f);
	}
	
	del[u]=1;
	for(int v:son[u])
		if(!e[v][f]) {
			g[v].insert(g[v].begin(),u);
			g[u].insert(g[u].begin(),f);
			For(i,1,n) son[i].clear(),fa[i]=dep[i]=del[i]=0; que.clear();
			dfs2(v,0);
			out(v,u);
			exit(0);
		}
//	assert(0);
	
	int v=son[u][0];
	for(int x:son[u])
		if(x!=v) g[u].insert(g[u].begin(),x);
	g[v].insert(g[v].begin(),u);
	For(i,1,n) son[i].clear(),fa[i]=dep[i]=del[i]=0; que.clear();
	dfs2(v,0);
	out(v,u);
	return 0;
}
/*

*/