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 "); 120 return 0; 121 } 122 Sort(); 123 124 if(!solve(st)) 125 printf("No Solution "); 126 else 127 cout << ans << endl; 128 129 return 0; 130 }