1 #include <bits/stdc++.h>
  2 #define dbg(x) cout << #x << "=" << x << endl
  3 #define eps 1e-8
  4 #define pi acos(-1.0)
  5 
  6 using namespace std;
  7 typedef long long LL;
  8 
  9 template<class T>inline void read(T &res)
 10 {
 11     char c;T flag=1;
 12     while((c=getchar())<‘0‘||c>‘9‘)if(c==‘-‘)flag=-1;res=c-‘0‘;
 13     while((c=getchar())>=‘0‘&&c<=‘9‘)res=res*10+c-‘0‘;res*=flag;
 14 }
 15 
 16 namespace _buff {
 17     const size_t BUFF = 1 << 19;
 18     char ibuf[BUFF], *ib = ibuf, *ie = ibuf;
 19     char getc() {
 20         if (ib == ie) {
 21             ib = ibuf;
 22             ie = ibuf + fread(ibuf, 1, BUFF, stdin);
 23         }
 24         return ib == ie ? -1 : *ib++;
 25     }
 26 }
 27 
 28 int qread() {
 29     using namespace _buff;
 30     int ret = 0;
 31     bool pos = true;
 32     char c = getc();
 33     for (; (c < ‘0‘ || c > ‘9‘) && c != ‘-‘; c = getc()) {
 34         assert(~c);
 35     }
 36     if (c == ‘-‘) {
 37         pos = false;
 38         c = getc();
 39     }
 40     for (; c >= ‘0‘ && c <= ‘9‘; c = getc()) {
 41         ret = (ret << 3) + (ret << 1) + (c ^ 48);
 42     }
 43     return pos ? ret : -ret;
 44 }
 45 
 46 const int maxn = 207;
 47 
 48 int n;
 49 
 50 int edge[maxn][maxn];
 51 int deg[maxn], fa[maxn];//出入度
 52 char ans[maxn*maxn];
 53 
 54 stack <char> s;
 55 
 56 int fid(int x) {
 57     return x == fa[x] ? x : fid(fa[x]);
 58 }
 59 
 60 void init() {
 61     for (int i = 64; i <= 128; ++i) {
 62         fa[i] = i;
 63     }
 64 }
 65 
 66 void dfs(int x) {
 67     for (int i = 64; i <= 128; ++i) {
 68         if(edge[x][i]) {
 69             edge[x][i] = edge[i][x] = 0;
 70             dfs(i);
 71         }
 72     }
 73     ans[n--] = x;
 74 }
 75 
 76 int main()
 77 {
 78     cin >> n;
 79     char a[5];
 80     int cnt = 0;
 81     init();
 82     for(int i = 1; i <= n; i++) {
 83         cin >> a;
 84         edge[a[0]][a[1]] = edge[a[1]][a[0]]=1;
 85         deg[a[0]]++;
 86         deg[a[1]]++;
 87         int x = fid(a[0]), y = fid(a[1]);
 88         fa[x]=y;
 89         //printf("x:fa[%d]:%d deg[%d]:%d\n",xx,fa[xx],a[0],deg[a[0]]);
 90         //printf("y:fa[%d]:%d deg[%d]:%d\n",yy,fa[yy],a[1],deg[a[1]]);
 91     }
 92     
 93     for (int i = 64; i <= 128; ++i) {
 94         
 95         if(fa[i] == i && deg[i]) {
 96             cnt++;
 97             //dbg(cnt);
 98         }
 99     }
100     //dbg(cnt);
101     if(cnt != 1) {//图不连通
102         puts("No Solution");
103         return 0;
104     }
105     //dbg(cnt);
106     cnt = 0;
107     int head = 0;
108     for (int i = 64; i <= 128; ++i) {
109         if(deg[i] & 1) {
110             cnt++;
111             if(!head)
112                 head = i;
113             //dbg(cnt);
114         }
115     }
116     if(cnt && cnt != 2) {
117         puts("No Solution");
118         return 0;
119     }
120     if(!head) {
121         for (int i = 64; i <= 128; ++i) {
122             if(deg[i]) {
123                 head = i;
124                 break;
125             }
126         }
127     }
128     dfs(head);
129     cout << ans << endl;
130     return 0;
131 }