#include <cstdio>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
const int MAXN = 200005;
#define rep(i, l, r) for (int i=(l); i<=(r); i++)
#define per(i, r, l) for (int i=(r); i>=(l); i--)

int N, M, fst[MAXN], fa[MAXN]; bool vis[MAXN];
vector<int> vec;
struct edge {
    int v, w, pre;
} e[MAXN<<1];
void adde(int a, int b, int c, int k) { e[k].v = b, e[k].w = c, e[k].pre = fst[a], fst[a] = k; }
int find(int x) { return x==fa[x] ? x : fa[x]=find(fa[x]); }

bool dfs(int x, int fa)
{
    vis[x] = 1;
    for (int o=fst[x]; o; o=e[o].pre) {
        int v = e[o].v;
        if (v==fa) continue;
        if (vis[v]) {
            vec.push_back(e[o].w);
            return 1;
        }
        vec.push_back(e[o].w);
        if (dfs(v, x)) return 1;
        vec.pop_back();
    }
    return 0;
}
int main()
{
    int T;
    for (scanf("%d", &T); T; T--) {
        scanf("%d%d", &N, &M);
        rep(i, 1, N) fst[i] = 0, fa[i] = i;
        int cir = 0, rt = 0;
        rep(i, 1, M) {
            int u, v; scanf("%d%d", &u, &v);
            if (!cir) adde(u, v, i, i), adde(v, u, i, i+M);
            int fu = find(u), fv = find(v);
            if (!cir) {
                if (fu!=fv) fa[fu] = fv;
                else cir = 1, rt = u;
            }
        }
        if (!cir) puts("-1");
        else {
            rep(i, 1, N) vis[i] = 0;
            vec.clear(), dfs(rt, 0);
            sort(vec.begin(), vec.end());
            int sz = vec.size();
            rep(i, 0, sz-2) printf("%d ", vec[i]);
            printf("%d\n", vec.back());
        }
    }
}