import sys
from functools import cmp_to_key

def compare(a, b):
    if a + b < b + a:
        return -1
    else:
        return 1

def main():
    n = int(sys.stdin.readline())
    strings = [sys.stdin.readline().strip() for _ in range(n)]
    
    current = [s for s in strings if s]
    result = []
    
    while current:
        # Determine the minimum current character
        min_char = min(s[0] for s in current)
        # Collect all candidates with the minimum character
        candidates = [s for s in current if s[0] == min_char]
        
        best_next = None
        best_combined = None
        
        for candidate in candidates:
            # Generate the new list after choosing this candidate
            new_list = []
            removed = False
            for s in current:
                if s == candidate and not removed:
                    # Take the rest of the string after removing the first character
                    rest = s[1:]
                    if rest:
                        new_list.append(rest)
                    removed = True
                else:
                    new_list.append(s)
            
            # Sort the new list using the custom comparator
            sorted_list = sorted(new_list, key=cmp_to_key(compare))
            combined = ''.join(sorted_list)
            
            current_combined = min_char + combined
            if best_combined is None or current_combined < best_combined:
                best_combined = current_combined
                best_next = candidate
        
        # Update current by removing the chosen character from best_next
        new_current = []
        removed = False
        for s in current:
            if s == best_next and not removed:
                rest = s[1:]
                if rest:
                    new_current.append(rest)
                removed = True
            else:
                new_current.append(s)
        # Remove any empty strings
        current = [s for s in new_current if s]
        result.append(min_char)
    
    print(''.join(result))

if __name__ == "__main__":
    main()