def  multiplication_table(start: int = 1 , end: int = 5) -> None:
    for i in range(start,end+1):
        print(f'multiplication_table for {i} ↓')
        print()
        for j in range(1,11):
            print(f'{i}*{j} : {i*j}')
        print()

def fahrenheit_to_celsius(fahrenheit_temperatures : int) -> str:
    celsius = (fahrenheit_temperatures - 32) * 5 / 9
    return f'Fahrenheit {fahrenheit_temperatures} -> Celsius : {celsius:.2f}'

def celsius_to_fahrenheit(celsius : int) -> str:
    fahrenheit = (celsius * 9/5) + 32
    return f'Celsius {celsius} -> fahrenheit : {fahrenheit:.2f}'

def finds_the_longest_word(sentence: str) -> str:
    longest_word = [word for word in sentence.split() if len(word) == len(max(sentence.split(),key=len))][0]
    return f'The longest word is : {longest_word}'

def main(num : int) -> int:
    boolean : bool = any("".join(char for char in str(num) if char in list("23456789")))
    if boolean:
        return -1
    else:
        last_digit : int = 0
        binary : int = 0
        power : int = 0
        while num != 0:
            last_digit = num%10
            binary = binary + (last_digit * 2 ** power)
            num = num//10
            power+=1
        return binary

def binary_to_decimal() -> None:
        binary_number : int = int(input("Enter the Binary Number : "))
        result : int = main(binary_number)
        if result == -1:
            print("You have entered a decimal number. Please enter a binary number instead.")
        else:
            print(f"The decimal of {binary_number} is {result}")
