/* Problem URL: https://cses.fi/problemset/task/1693 */

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template <class T, class comp = less<>>
using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;

#define V vector

#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)

#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)

#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()

using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;

using ll = long long;

using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;

template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
    os << vec[0];
    for (size_t i = 1; i < vec.size(); i++) {
        os << ' ' << vec[i];
    }
    os << '\n';
    return os;
}

template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
    for (auto &i : vec) {
        is >> i;
    }
    return is;
}

template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
    for (auto &i : vec) {
        os << i[0];
        for (size_t j = 1; j < i.size(); j++) {
            os << ' ' << i[j];
        }
        os << '\n';
    }
    return os;
}

template<class v>
auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
    for (auto &i : vec) {
        for (auto &j : i) {
            is >> j;
        }
    }
    return is;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;

    vi out(n);
    vi in(n);

    vvi graph(n);

    while (m--) {
        int a, b;
        cin >> a >> b;
        a--, b--;

        out[a]++;
        in[b]++;
        
        graph[a].push_back(b);
    }

    auto check = [&]() {
        if (out[0] != in[0] + 1 || out[n - 1] + 1 != in[n - 1]) {
            return false;
        };

        nrep(i, 1, n - 1) {
            if (out[i] != in[i]) {
                return false;
            }
        }

        return true;
    };

    if (!check()) {
        cout << "IMPOSSIBLE\n";
        return 0;
    }
    
    stack<int> s;
    s.push(0);

    vi path;
    
    while (!s.empty()) {
        int i = s.top();

        if (graph[i].empty()) {
            path.push_back(i + 1);
            s.pop();
            continue;
        }

        s.push(graph[i].back());
        graph[i].pop_back();
    }

    rep(i, n) {
        if (!graph[i].empty()) {
            cout << "IMPOSSIBLE\n";
            return 0;
        }
    }

    reverse(all(path));

    cout << path;
}