#include<cstdio>

 #include<iostream>

 using namespace std;

 int ans[],du[],n,k = 0x7f7f7f,b[][],cnt = 0x3f,bj,tot;

 string l;

 inline void dfs(int x) {

     for(int i = ;i < ; i++)

         if(b[x][i]) {

             b[x][i] = b[i][x] = ;

             dfs(i);

         }

     ans[++tot] = x;

 }

 int main()

 {

     scanf("%d",&n);

     for(int i = ;i <= n; i++) {

         int x,y;

         cin >> l;

         x = l[] - 'A';

         y = l[] - 'A';

         k = min(k,min(x,y));

         b[x][y] = b[y][x] = ;

         du[x]++;

         du[y]++;

     }

     for(int i = ;i < ; i++)

         if(du[i] %  == ) {

             bj++;

             cnt = min(cnt,i);

         }

     if(bj == ) dfs(k);

     else if(bj == ) dfs(cnt);

     else {

         printf("No Solution");

         return ;

     }

     for(int i = tot;i >= ; i--)

         printf("%c",ans[i] + 'A');

     return ;

 }