def number_to_excel_column(n):
    # Check if n is an integer
    if not isinstance(n, int):
        return "Invalid Input"
    # Check constraints
    if n < 0:
        return -1
    if n == 0:
        return "Invalid Input"

    column_name = ""
    while n > 0:
        n -= 1  # Adjust for 1-based indexing
        remainder = n % 26
        column_name = chr(65 + remainder) + column_name
        n //= 26
    return column_name


# Example usage:
try:
    user_input = input().strip()
    if not user_input.lstrip('-').isdigit():
        print("Invalid Input")
    else:
        num = int(user_input)
        print(number_to_excel_column(num))
except Exception:
    print("Invalid Input")