#include <bits/stdc++.h>

#define PII pair<int,int>

#define fi first

#define se second

using namespace std;

const int N = 100010;

int n, m, fa[N], stk[N], top;

vector<PII> v[N];

bool vis[N], mark;

int find(int x)

{

    return fa[x] == x ? x : fa[x] = find(fa[x]);

}

void dfs(int u, int pre, int ed)

{

    if(mark) return;

    if(u == ed && ~pre) {

        mark = true;

        sort(stk + 1, stk + 1 + top);

        for(int i = 1; i <= top; i++) printf("%d ", stk[i]);

        cout << endl;

    }

    for(auto i : v[u]) {

        if(vis[i.fi] || i.fi == pre) continue;

        stk[++top] = i.se, vis[i.fi] = true;

        dfs(i.fi, u, ed);

        -- top, vis[i.fi] = false;

    }

}

void solve()

{

    cin >> n >> m;

    for(int i = 1; i <= n; i++) {

        fa[i] = i, vis[i] = false;

        v[i].clear();

    }

    int st = 0;

    bool flag = false;  // 是否存在环

    for(int i = 1; i <= m; i++) {

        int x, y;

        scanf("%d%d", &x, &y);

        if(flag) continue;

        v[x].push_back({y, i}), v[y].push_back({x, i});

        int fx = find(x), fy = find(y);

        if(fx == fy) flag = true, st = x;

        else fa[fx] = fy;

    }

    if(!flag) puts("-1");

    else mark = false, dfs(st, -1, st);

}

int main()

{

    int test;

    cin >> test;

    while(test--) solve();

    return 0;

}