#include<cstdio>
#include<vector>
#include<algorithm>
#include<functional>
using namespace std;

int N, M, used[100001];

struct set_graph{
	vector<int> v;
}sg[100001];

vector<int>res;


void Input() {
	int a, b;
	FILE*in = fopen("maxpath.in", "r");
	fscanf(in, "%i %i\n", &N, &M);
	for (int i = 1; i <= M; i++) {
		fscanf(in, "%i %i\n", &a, &b);
		sg[a].v.push_back(b); sg[b].v.push_back(a);
	}
}

void Solve(){
	int V = N, kon = 0; used[V]++;
	for (int i = 1; i <= N; i++) {
		sort(sg[i].v.begin(), sg[i].v.end(), greater<int>());
	}
	res.push_back(V);
	while (kon == 0) {
		for (int i = 0; i < 100001; i++) {
			if (used[sg[V].v[sg[V].v.size() - 1]]) { kon++; break; }
			if (used[sg[V].v[i]] > 0)continue;
			used[sg[V].v[i]]++; V = sg[V].v[i]; res.push_back(V); break;
		}
	}
}

void Output(){
	FILE *out = fopen("maxpath.out", "w");
	fprintf(out, "%i\n", res.size());
	for (int i = res.size() - 1; i >= 0; i--) {
		fprintf(out, "%i\n", res[i]);
	}
}

int main(){

	Input();
	Solve();
	Output();
	
	return 0;
}