import bisect
import sys
# sys.stdin = open("1.in", "r")
sys.setrecursionlimit(int(5e5) + 1)
n, m = map(int, input().split())
paths = [set() for _ in range(n)]
for _ in range(m):
a, b = map(lambda x: int(x) - 1, input().split())
paths[a].add(b)
paths[b].add(a)
res = []
def solve(node):
while paths[node]:
top = paths[node].pop()
paths[top].discard(node)
solve(top)
res.append(node)
solve(0)
next = [[] for _ in range(n)]
for i in range(len(res)): next[res[i]].append(i)
nested = [[]]
ends = [len(res) - 1]
for i in range(len(res)):
if ends[-1] == i:
ends.pop()
print(*nested.pop())
continue
nested[-1].append(res[i] + 1)
less = bisect.bisect_left(next[res[i]], ends[-1]) - 1
if next[res[i]][less] != i:
nested.append([res[i] + 1])
ends.append(next[res[i]][less])
