To solve this problem, you can iterate through each of the strings and use a set to store the unique characters in each string. Then, you can find the string with the minimum number of unique characters and return the string with the minimum lexicographical order among those strings.

# Get the number of strings
n = int(input())

# Initialize the minimum number of unique characters and the result string
min_unique = float('inf')
result = ""

# Iterate through each string
for i in range(n):
  # Get the current string
  s = input()

  # Convert the string to a set and find the number of unique characters
  unique_chars = len(set(s))

  # Update the minimum number of unique characters and result string if necessary
  if unique_chars < min_unique:
    min_unique = unique_chars
    result = s
  elif unique_chars == min_unique:
    result = min(result, s)

# Print the result
print(result)