#include <cstdio>
#include <vector>
#include <stack>

using namespace std;

const int kMaxN = 100005;

vector<int> G[kMaxN];
int N, M;
stack<int> Stack, Cycle;

inline void Delete(const int X, const int Y) {
    G[X].pop_back();
    for (vector<int>::iterator v = G[Y].begin(); v != G[Y].end(); ++v) {
        if (*v == X) {
            G[Y].erase(v);
            return;
        }
    }
}

inline void Euler(int X) {
    for (int Y; !G[X].empty(); Y = G[X].back(), Delete(X, Y), X = Y)
        Stack.push(X);
}

bool EulerianCycle() {
    for (int i = 1; i <= N; ++i)
        if (G[i].size()&1)
            return false;

    int X = 1;
    do {
        Euler(X);
        X = Stack.top(); Stack.pop();
        Cycle.push(X);
    }
    while(!Stack.empty());

    if (Cycle.size() <= M)
        return false;
    return true;
}

void Read() {
    freopen("ciclueuler.in", "r", stdin);
    scanf("%d %d", &N, &M);
    for (; M; --M) {
        int X, Y; scanf("%d %d", &X, &Y);
        G[X].push_back(Y);
        G[Y].push_back(X);
    }
}

void Print() {
    freopen("ciclueuler.out", "w", stdout);
    if (!EulerianCycle()) {
        printf("-1\n");
        return;
    }
    for (; !Cycle.empty(); Cycle.pop())
        printf("%d ", Cycle.top());
    printf("\n");
}

int main() {
    Read();
    Print();
    return 0;
}