#include <iostream>
#include <vector>
#include <set>
using namespace std;

vector <string> grid ;
vector < vector<char> > depend(26) ;
string result ;
bool vis[26] = {false};

void dfs(char c) ;
void check (int r ,int c);

int main( int argc, char ** argv ) {
	string s ;
	while(cin >> s)
	{
	while(s != "#")
	{
		grid.push_back(s) ;
		cin >> s ;
	}
	set <char> ss ;
	for(int i = 0;i < grid.size();i++)
		for(int j = 0,n = grid[i].length();j < n;j++)
			ss.insert(grid[i][j]);
	int r = grid.size()-1 ;
	check(r,0) ;
	for(auto it = ss.begin();it != ss.end();it++)
		if(!vis[*it-'A'])
			dfs(*it) ;
	cout << result << endl;
	grid.clear() ;
	for(int i = 0;i < 26;i++)
		depend[i].clear() ;
	fill_n(vis,26,0) ;
	}
	return 0;
}

void check (int r ,int c)
{
	if(r == 0)
		return ;
	if(c == min(grid[r].length(),grid[r-1].length())){
		check(r-1,0) ;
		return ;
	}
	if(grid[r][c] == grid[r-1][c])
		check(r,c+1) ;
	if(grid[r][c] != grid[r-1][c])
	{
		depend[grid[r][c]-'A'].push_back(grid[r-1][c]) ;
		check(r-1,0) ;
	}
}

void dfs(char c)
{
	vis[c-'A'] = true ;
	for(int i = 0;i < depend[c-'A'].size();i++)
	{
		char child = depend[c-'A'][i] ;
		if(!vis[child-'A'])
			dfs(child) ;
	}
	result += c;
}