import sys
from functools import lru_cache

def main():
    sys.setrecursionlimit(1 << 25)
    n = int(sys.stdin.readline())
    strings = [sys.stdin.readline().strip() for _ in range(n)]

    @lru_cache(maxsize=None)
    def dfs(state):
        remaining = [s for s in state if s]
        if not remaining:
            return ''
        first_chars = [s[0] for s in remaining]
        min_char = min(first_chars)
        candidates_indices = [i for i, s in enumerate(state) if s and s[0] == min_char]
        min_str = None
        for idx in candidates_indices:
            new_state = list(state)
            new_state[idx] = new_state[idx][1:]
            new_state_tuple = tuple(new_state)
            res = min_char + dfs(new_state_tuple)
            if min_str is None or res < min_str:
                min_str = res
        return min_str

    initial_state = tuple(strings)
    print(dfs(initial_state))

if __name__ == '__main__':
    main()