#include<bits/stdc++.h>
using namespace std;
const int N=2e5+5;
int n,m,ax[N],ay[N],d[N],ned[N],l1[N];
int prt[N];
vector<int>bel[N],tr[N];
int gf(int x){if(x==prt[x])return x;return prt[x]=gf(prt[x]);}
void merge(int x,int y){x=gf(x),y=gf(y);if(x!=y)prt[x]=y;}
struct abc{int a,b;};
struct abcd{int to,a;};
vector<abc>op[N],ans;
vector<abcd>son[N],son1[N];
int st[N],top,pos[N],ad[N];
vector<int>all,oth[N];
bool cmp(int a,int b){return ned[a]<ned[b];}
int temp[4];
struct ab
{
	int pos,cd,tag;
	bool operator < (const ab &a) const
	{
		if(cd!=a.cd)return cd>a.cd;
		return tag>a.tag;
	}
};
bool vis[N];
int tot;
void dfs(int x)
{
	vis[x]=1,pos[x]=++tot;bool fl=0;
	for(auto y:son[x])if(!vis[y.to])dfs(y.to),fl=1;
	if(!fl)for(auto y:son1[x])if(!vis[y.to])dfs(y.to);
}
int ct;
void solve()
{
	ans.clear(),all.clear();
	for(int i=1;i<=n;i++)son[i].clear(),bel[i].clear(),op[i].clear(),prt[i]=i,son1[i].clear();
	for(int i=1;i<=n;i++)pos[i]=0,vis[i]=0,ad[i]=0,ax[i]=0,ay[i]=0,d[i]=0,ned[i]=0,oth[i].clear(),tr[i].clear(),pos[i]=0;
	for(int i=1;i<=m;i++)l1[i]=0;
	for(int i=1;i<=m;i++)
	{
		int x,y,len;
		scanf("%d",&len),l1[i]=len;
		if(len==1)
		{
			scanf("%d",&x);
			if(!ax[x])ax[x]=i;else ay[x]=i;
		}
		else if(len==2)
		{
			scanf("%d %d",&x,&y);
			son[y].push_back((abcd){x,i}),merge(x,y),d[x]++;
			son1[x].push_back((abcd){y,i});
			ad[x]++,ad[y]++;
			if(!ax[x])ax[x]=i;else ay[x]=i;
			if(!ax[y])ax[y]=i;else ay[y]=i;
		}
	}
	for(int i=1;i<=n;i++)bel[gf(i)].push_back(i);
	st[1]=-3,st[2]=-2,st[3]=-1,top=3;
	for(int i=1;i<=n;i++)if(gf(i)==i)
	{
		priority_queue<ab>q;
		tot=0;
		int rt=bel[i][0];
		for(auto j:bel[i])if(ad[j]==1)rt=j;
		dfs(rt);
		for(auto j:bel[i])if(d[j]==0)q.push((ab){j,(int)son[j].size(),pos[j]});
		if(!q.size())
		{
			if(bel[i].size()==1)continue;
			ned[i]=1;
			int len=bel[i].size();
			int x=bel[i][0];
			op[i].push_back((abc){son1[x][0].a,-1});
			int y=son1[x][0].to;
			int now=x,lst=son1[x][0].a;
			while(son[now][0].to!=x)op[i].push_back((abc){son[now][0].a,lst}),lst=son[now][0].a,now=son[now][0].to;
			op[i].push_back((abc){lst,-1});
			all.push_back(i),oth[i].push_back(lst);
			continue;
		}
		while(!q.empty())
		{
			int x=q.top().pos;q.pop();
			if(son[x].size()==2)
			{
				op[i].push_back((abc){ax[x],st[top]});
				op[i].push_back((abc){ay[x],st[top]});
				top--;
			}
			else if(son[x].size()==1)
			{
				int pos=son[x][0].a,pos1;
				if(ax[x]!=pos)pos1=ax[x];else pos1=ay[x];
				op[i].push_back((abc){pos,pos1});
			}
			else
			{
				op[i].push_back((abc){ax[x],ay[x]});
				st[++top]=ax[x];
			}
			for(auto y:son[x])
			{
				d[y.to]--;
				if(!d[y.to])q.push((ab){y.to,(int)son[y.to].size(),pos[y.to]});
			}
		}
		while(top && st[top]>0)oth[i].push_back(st[top]),top--;
		ned[i]=-st[top]-1;
		all.push_back(i);
		st[1]=-3,st[2]=-2,st[3]=-1,top=3;
	}
	sort(all.begin(),all.end(),cmp);
	top=0;
	for(int i=1;i<=m;i++)if(!l1[i])st[++top]=i;
	for(auto i:all)
	{
		if(ned[i]>top){printf("-1\n");return ;}
		for(int j=1;j<=ned[i];j++)temp[j]=st[top-j+1];
		top-=ned[i];
		for(auto &j:op[i])
		{
			if(j.a<0)j.a=temp[-j.a];
			if(j.b<0)j.b=temp[-j.b];
		}
		for(auto j:op[i])ans.push_back(j);
		for(auto j:oth[i])st[++top]=j;
	}
	printf("%d\n",(int)ans.size());
	for(auto j:ans)printf("%d %d\n",j.a,j.b);
}
int main()
{
	// freopen("cluster.in","r",stdin);
	// freopen("cluster.out","w",stdout);
	while(~scanf("%d %d",&n,&m))solve();
	return 0;
}