import string

# Sample data
n = 3
names = ["Meher", "Govindh", "Pavni"]

# Data structure to store visitor names
visitor_list = []

# Allowed characters: letters and digits only
allowed_chars = string.ascii_letters + string.digits

# Flag to check for invalid input
is_valid = True

# Process each name
for name in names:
    if all(char in allowed_chars for char in name):
        visitor_list.append(name)
    else:
        is_valid = False
        break

# Final output stored in this variable
output = "Invalid input" if not is_valid else " ".join(visitor_list)