1 #include <set>
 2 #include <map>
 3 #include <queue>
 4 #include <stack>
 5 #include <cmath>
 6 #include <bitset>
 7 #include <cstdio>
 8 #include <string>
 9 #include <vector>
10 #include <cstdlib>
11 #include <cstring>
12 #include <iostream>
13 #include <algorithm>
14 using namespace std;
15
16 typedef long long ll;
17 typedef pair<ll, ll> pll;
18 typedef pair<ll, int> pli;
19 typedef pair<int, ll> pil;;
20 typedef pair<int, int> pii;
21 typedef unsigned long long ull;
22
23 #define lson i<<1
24 #define rson i<<1|1
25 #define bug printf("*********\n");
26 #define FIN freopen("D://code//in.txt", "r", stdin);
27 #define debug(x) cout<<"["<<x<<"]" <<endl;
28 #define IO ios::sync_with_stdio(false),cin.tie(0);
29
30 const double eps = 1e-8;
31 const int mod = 10007;
32 const int maxn = 1e6 + 7;
33 const double pi = acos(-1);
34 const int inf = 0x3f3f3f3f;
35 const ll INF = 0x3f3f3f3f3f3f3f;
36
37 int s, u, v, t, mx, p;
38 int mp[55][2007], in[55], vis[2007], ans[2007];
39
40 void eulergraph(int s) {
41     for(int i = 1; i <= mx; i++) {
42         if(mp[s][i] && !vis[i]) {
43             vis[i] = 1;
44             eulergraph(mp[s][i]);
45             ans[++p] = i;
46         }
47     }
48 }
49
50 int main() {
51     //FIN;
52     while(~scanf("%d%d", &u, &v)) {
53         if(u == 0 && v == 0) break;
54         s = min(u, v);
55         p = 0;
56         memset(in, 0, sizeof(vis));
57         memset(mp, 0, sizeof(mp));
58         memset(vis, 0, sizeof(vis));
59         scanf("%d", &t);
60         in[u]++, in[v]++;
61         mx = t;
62         mp[u][t] = v, mp[v][t] = u;
63         while(~scanf("%d%d", &u, &v)) {
64             if(u == 0 && v == 0) break;
65             scanf("%d", &t);
66             mx = max(mx, t);
67             in[u]++, in[v]++;
68             mp[u][t] = v, mp[v][t] = u;
69         }
70         int flag = 0;
71         for(int i = 1; i <= 45; i++) {
72             if(in[i] & 1) {
73                 printf("Round trip does not exist.\n");
74                 flag = 1;
75                 break;
76             }
77         }
78         if(flag) continue;
79         eulergraph(s);
80         for(int i = p; i >= 1; i--) {
81             printf("%d%c", ans[i], i == 1 ? '\n' : ' ');
82         }
83     }
84     return 0;
85 }