#include<bits/stdc++.h>
#define ull unsigned long long
#define ui unsigned int
#define ld long double
#define ll long long
#define lll __int128
#define fi first
#define se second
#define e emplace
#define eb emplace_back
#define db double
#define ef emplace_front
#define pii pair<int,int>
#define pll pair<ll,ll>
#define vi vector<int>
#define vp vector<pii>
#define vt vector<tup>
#define all(x) x.begin(),x.end()
#define mp make_pair

#define FastI
#define FastO
#define int ll
bool ST;
static const ll MOD=1e9+7,Phi=998244352,inv2=499122177,Root=3,iRoot=332748118;
static const ll inf=1073741823,Inf=4294967296,INF=1e18;
static const ld eps=1e-9,pi=3.1415926535;
char in[1<<20],*p1=in,*p2=in;
char out[1<<20],*p3=out;
using namespace std;
struct tup
{
	int x,y,z;
	tup(int X=0,int Y=0,int Z=0)
	{x=X,y=Y,z=Z;}
	bool operator <(const tup nd)const
	{return x<nd.x;}
};
#ifdef FastI
#define getchar() (p1==p2&&(p2=(p1=in)+fread(in,1,1<<20,stdin),p1==p2)?EOF:*p1++)
#endif
#ifdef FastO
#define putchar(x) (p3-out==1<<20?fwrite(out,1,1<<20,stdout),p3=out,0:0,*p3++=x)
#define puts(x) write(x,'\n')
#endif
namespace FastIO
{
	template<typename T> inline void write(T x,char ch=' ')
	{
		if(is_same<char,T>::value)putchar(x);
		else
		{
			if(x<0)x=-x,putchar('-');
			static char st[25];
			int top=0;
			do st[top++]=x%10+'0',x/=10;while(x);
			while(top)putchar(st[--top]);
		}
		ch!='~'?putchar(ch):0;
	}
	inline void write(const char*x,char ch=' ')
	{
		for(int i=0;x[i]!='\0';++i)putchar(x[i]);
		ch!='~'?putchar(ch):0;
	}
	inline void read(char&s){do s=getchar();while(s=='\n'||s==' ');}
	inline void read(char s[])
	{
		int len=0;char st;
		do st=getchar();while(st=='\n'||st==' ');
		s[++len]=st,st=getchar();
		while(st!='\n'&&st!=' '&&st!='\r')s[++len]=st,st=getchar();
		s[++len]='\0';
	}
	template<typename T> inline void read(T &s)
	{
		char ch=getchar();s=0;
		while((ch>'9'||ch<'0')&&ch!='-')ch=getchar();
		bool tf=(ch=='-'&&(ch=getchar()));
		while(ch>='0'&&ch<='9')s=(s<<1)+(s<<3)+ch-'0',ch=getchar();
		s=tf?-s:s;
	}
	inline void edl(){putchar('\n');}
	template<typename T1,typename T2> inline void read(pair<T1,T2> &s){read(s.fi),read(s.se);}
	template<typename T,typename...Args> inline void write(T x,Args...args){write(x,'~'),write(args...);}
	template<typename T,typename...Args> inline void read(T&x,Args&...args){read(x),read(args...);}
	#ifdef FastO
	struct Writer{~Writer(){fwrite(out,1,p3-out,stdout);}}Writ;
	#endif
}
using namespace FastIO;
namespace MTool
{
	inline int Cadd(int a,int b){return (ll)a+b>=MOD?(ll)a+b-MOD:a+b;}
	inline int Cdel(int a,int b){return a-b<0?a-b+MOD:a-b;}
	inline int Cmul(int a,int b){return 1ll*a*b%MOD;}
	inline int sqr(int a){return 1ll*a*a%MOD;}
	inline void Madd(int&a,int b){a=((ll)a+b>=MOD?(ll)a+b-MOD:a+b);}
	inline void Mdel(int&a,int b){a=(a-b<0?a-b+MOD:a-b);}
	inline void Mmul(int&a,int b){a=1ll*a*b%MOD;}
	inline int Cmod(int x){return (x%MOD+MOD)%MOD;}
	inline void Mmod(int&x){x=(x%MOD+MOD)%MOD;}
	template<typename T> inline bool Mmax(T&a,T b){return a<b?a=b,1:0;}
	template<typename T> inline bool Mmin(T&a,T b){return a>b?a=b,1:0;}
	template<typename...Args> inline void Madd(int&a,int b,Args...args){Madd(a,b),Madd(a,args...);}
	template<typename...Args> inline void Mmul(int&a,int b,Args...args){Mmul(a,b),Mmul(a,args...);}
	template<typename...Args> inline void Mdel(int&a,int b,Args...args){Mdel(a,b),Mdel(a,args...);}
	template<typename...Args> inline int Cadd(int a,int b,Args...args){return Cadd(Cadd(a,b),args...);}
	template<typename...Args> inline int Cmul(int a,int b,Args...args){return Cmul(Cmul(a,b),args...);}
	template<typename...Args> inline int Cdel(int a,int b,Args...args){return Cdel(Cdel(a,b),args...);}
	template<typename...Args,typename T> inline bool Mmax(T&a,T b,Args...args){return Mmax(a,b)|Mmax(a,args...);}
	template<typename...Args,typename T> inline bool Mmin(T&a,T b,Args...args){return Mmin(a,b)|Mmin(a,args...);}
	inline int power(int x,int y){int s=1;for(;y;y>>=1,Mmul(x,x))if(y&1)Mmul(s,x);return s;}
}
using namespace MTool;
namespace WrongAnswer_90
{
	int n,m;
	int deg[4010];
	pii edge[4010];
	bool del[4010],vis[4010];
	vi L,R;
	map<pii,int> hash;
	
	const int N=4000,M=8000;
    int cnt=1,num,col,low[N+10],dfn[N+10],head[N+10],to[M+10],nex[M+10],c[N+10];
    inline void add(int x,int y){to[++cnt]=y,nex[cnt]=head[x],head[x]=cnt;}
    stack<int> st;
    void tarjan(int x,int fromi)
    {
        dfn[x]=low[x]=++num,st.e(x);
        for(int i=head[x];i;i=nex[i])
        {
            if(i==(fromi^1))continue;
            if(!dfn[to[i]])
			{
				tarjan(to[i],i),low[x]=min(low[x],low[to[i]]);
				if(low[to[i]]>dfn[x])
				{
					del[hash[mp(x,to[i])]]=1;
					L.eb(hash[mp(x,to[i])]);
				}
			}
            else low[x]=min(low[x],dfn[to[i]]);
        }
        if(low[x]==dfn[x])
        {
            int y;++col;
            do y=st.top(),c[y]=col,st.pop();while(y!=x);
        }
    }
	
	void mian()
	{
		int x,y;
		hash.clear();
		L.clear(),R.clear();
		memset(del,0,sizeof(del));
		read(n,m);
		for(int i=1;i<=m;++i)
		{
			read(x,y),edge[i]=mp(x,y);
			hash[mp(x,y)]=hash[mp(y,x)]=i;
		}
		while(L.size()+R.size()<m)
		{
			int pre=L.size()+R.size();
			cnt=1,memset(head,0,sizeof(head)),memset(dfn,0,sizeof(dfn));
			for(int i=1;i<=m;++i)if(!del[i])
			add(edge[i].fi,edge[i].se),add(edge[i].se,edge[i].fi);
			for(int i=1;i<=n;++i)if(!dfn[i])tarjan(i,0);
			memset(vis,0,sizeof(vis)),memset(deg,0,sizeof(deg));
			for(int i=1;i<=m;++i)if(!del[i])
			++deg[edge[i].fi],++deg[edge[i].se];
			for(int i=1;i<=m;++i)if(!vis[c[edge[i].fi]])
			{
				if(deg[edge[i].fi]==2&&deg[edge[i].se]==2)
				del[i]=1,vis[c[edge[i].fi]]=1,R.eb(i);
			}
			if(L.size()+R.size()==pre)
			return puts("-1"),void();
		}
		reverse(all(R));
		for(auto p:L)write(p);
		for(auto p:R)write(p);
		puts("");
	}
	inline void Mian()
	{
		int T=1,C;
		read(T);
		while(T--)mian();
	}
}
bool ED;
signed main()
{
//	ios::sync_with_stdio(0);
//	freopen("1.in","r",stdin);
//	freopen("1.out","w",stdout);
	WrongAnswer_90::Mian();
	return 0;
}