n,m = [int(i) for i in input().split()]
g = [[] for i in range(n+1)]
for i in range(m):
    x,y = [int(i) for i in input().split()]
    g[x].append(y)
    g[y].append(x)

visited = [False]*(n+1)

def dfs(v,b):
    visited[v] = True
    if b: print(v,end=' ')
    for w in g[v]:
        if not visited[w]:
            dfs(w, not b)
    if not b: print(v,end=' ')

dfs(1,True)
print()