#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ul unsigned ll
#define LL __int128_t
#define db double
#define DB long db
#define pii pair<int, int>
#define pil pair<int, ll>
#define fi first
#define se second
#define mkpr make_pair
#define vi vector<int>
#define vii vector<pii>
#define vil vector<pil>
#define eb emplace_back
#define all(c) (c).begin(), (c).end()
#define bit(x) (1 << (x))
#define bin(s, x) ((s) >> (x) & 1)
#define mem(a, x) memset(a, x, sizeof(a))
#define req(i, l, r) for (int i(l), i##End(r); i < i##End; i = -~i)
#define qer(i, r, l) for (int i(r), i##End(l); i > i##End; i = ~-i)
#define rep(i, l, r) for (int i(l), i##End(r); i <= i##End; i = -~i)
#define per(i, r, l) for (int i(r), i##End(l); i >= i##End; i = ~-i)

#ifdef JYR
#define errs(x) fputs(x "\n", stderr)
#define errm(x, ...) fprintf(stderr, x, ##__VA_ARGS__)
#else
#define errs(x) 0
#define errm(x, ...) 0
#endif

template<typename T, typename U> void chkmx(T &_a, U _b) { if (_a < _b) _a = _b; }
template<typename T, typename U> void chkmn(T &_a, U _b) { if (_a > _b) _a = _b; }
template<typename T> T sq(T x) { return x * x; }

bool Mbe;

#define MC

#define N 4005
#define mod 998244353
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f3f3f

int n, m;
vii G[N];
vi ans, res, tmp;
struct { int u, v, id; } e[N];
bool vs[N];
int dfn[N], low[N], tot;

void tarjan(int u, int t) {
    dfn[u] = low[u] = ++tot;
    for (auto [v, i] : G[u]) {
        if (!dfn[v]) tarjan(v, i), chkmn(low[u], low[v]);
        else if (i != t) chkmn(low[u], dfn[v]);
    }
    if (t && dfn[u] == low[u]) tmp.eb(t);
}

void mslv() {
    scanf("%d%d", &n, &m);
    rep(i, 1, m) {
        int u, v;
        scanf("%d%d", &u, &v);
        e[i] = {u, v, i}, vs[i] = 0;
    }
    ans.clear(), res.clear();
    rep(_, 1, m) {
        rep(i, 1, n) G[i].clear();
        rep(i, 1, m) if  (!vs[i]) {
            auto [u, v, id] = e[i];
            G[u].eb(v, id), G[v].eb(u, id);
        }
        bool fg = 0;
        rep(i, 1, m) if (!vs[i]) {
            auto [u, v, id] = e[i];
            if (G[u].size() <= 2 && G[v].size() <= 2) {
                vs[i] = fg = 1, res.eb(id);
                break;
            }
        }
        errm("Round %d:\n", _);
        rep(i, 1, m) if (!vs[i]) errm("[%d %d %d]\n", e[i].u, e[i].v, e[i].id);
        errs("res:");
        for (auto i : res) errm("%d ", i);
        errs("");
        if (fg) continue;
        tot = 0, tmp.clear();
        rep(i, 1, n) dfn[i] = 0;
        rep(i, 1, n) if (!dfn[i]) tarjan(i, 0);
        if (!tmp.empty()) vs[tmp[0]] = 1, ans.eb(tmp[0]);
        rep(u, 1, n) {
            errm("%d: %d %d\n", u, dfn[u], low[u]);
            for (auto [v, i] : G[u]) errm(" | %d %d", v, i);
            errs("");
        }
        errs("ans:");
        for (auto i : ans) errm("%d ", i);
        errs("");
        errs("tmp:");
        for (auto i : tmp) errm("%d ", i);
        errs("");
    }
    for (auto i : std::views::reverse(res)) ans.eb(i);
    if (ans.size() != m) puts("-1");
    else {
        for (auto i : ans) printf("%d ", i);
        puts("");
    }
    for (auto i : ans) errm("%d ", i);
    errs("");
}

void mprw() {}

bool Med;

int main() {
    #ifdef JYR
    freopen("Test.in", "r", stdin);
    freopen("Test.out", "w", stdout);
    #endif
    mprw();
    #ifdef MC
    int _; scanf("%d", &_);
    while (_--) mslv();
    #else
    mslv();
    #endif
    errm("%.3lfMB %.0lfms\n", abs(&Med - &Mbe) / 1048576., clock() * 1000. / CLOCKS_PER_SEC);
    return 0;
}