1 #include <bits/stdc++.h>
2 #define _for(i,a,b) for(int i = (a);i < b;i ++)
3 #define _rep(i,a,b) for(int i = (a);i > b;i --)
4 #define INF 0x3f3f3f3f
5 #define pb push_back
6 typedef long long ll;
7 using namespace std;
8 inline ll read()
9 {
10 ll ans = 0;
11 char ch = getchar(), last = ' ';
12 while(!isdigit(ch)) last = ch, ch = getchar();
13 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
14 if(last == '-') ans = -ans;
15 return ans;
16 }
17 inline void write(ll x)
18 {
19 if(x < 0) x = -x, putchar('-');
20 if(x >= 10) write(x / 10);
21 putchar(x % 10 + '0');
22 }
23
24 int sc4(char c)
25 {
26 if(islower(c))
27 return c-'a'+26;
28 else
29 return c-'A';
30 }
31 int sc3(int k)
32 {
33 if(k<=25)
34 return 'A'+k;
35 else
36 return 'a'+k-26;
37 }
38 int N;
39 vector<vector<int>> v(100);
40 int vis[100][100];
41 string ans;
42 bool dfs(int nw)
43 {
44 if(ans.size()==N+1)
45 return true;
46
47 _for(i,0,v[nw].size())
48 {
49 if(vis[nw][v[nw][i]]>0)
50 {
51 vis[nw][v[nw][i]] --;
52 vis[v[nw][i]][nw] --;
53 ans += sc3(v[nw][i]);
54 if(dfs(v[nw][i])) return true;
55 vis[v[nw][i]][nw] ++;
56 vis[nw][v[nw][i]] ++;
57 ans.pop_back();
58 }
59 }
60 return false;
61 }
62
63 bool solve(int st)
64 {
65 ans += sc3(st);
66 if(dfs(st))
67 return true;
68 ans.pop_back();
69 return false;
70 }
71
72 void Sort()
73 {
74 _for(i,0,99)
75 sort(v[i].begin(),v[i].end());
76 }
77 int judge()
78 {
79 int odd = 0;
80 int st = -1;
81 _for(i,0,60)
82 {
83 int sum = 0;
84 _for(j,0,60)
85 {
86 sum += vis[i][j];
87 }
88 if(sum&0x1)
89 {
90 if(st==-1)
91 st = i;
92 odd ++;
93 }
94 }
95 if(odd!=0 && odd!=2)
96 return -1;
97 else if(!odd)
98 return 0;
99 else
100 return st;
101 }
102 int main()
103 {
104 N = read();
105
106 _for(i,0,N)
107 {
108 char c1,c2;
109 cin >> c1 >> c2;
110 v[sc4(c1)].pb(sc4(c2));
111 v[sc4(c2)].pb(sc4(c1));
112 vis[sc4(c1)][sc4(c2)]++;
113 vis[sc4(c2)][sc4(c1)]++;
114 }
115
116 int st = judge();
117 if(st==-1)
118 {
119 printf("No Solution\n");
120 return 0;
121 }
122 Sort();
123
124 if(!solve(st))
125 printf("No Solution\n");
126 else
127 cout << ans << endl;
128
129 return 0;
130 }
