def extra$\_$credit$\_$problem$\_1()$:

$$ start$\_$year $=1900$

$$ end$\_$year $=2100$

$$ # TODO: Write a program to print leap years from the year $1900$ to $2100$

$$ # $5$ points extra credits

$$ pass

def extra$\_$credit$\_$problem$\_2($n$)$:

$$ # a prime number is a natural number greater than $1,$ that can only divisible by itself and $1$

$$ # $10$ points extra credits

$$ # TODO: given the number n$,$ check if n is a prime number

$$ pass

def main$()$:

$$ print$\_$hello$()$

$$ # prompt user to get the input then call functions

$$ # $...$

$$

main$()$