def linear_combination(x, y):
    y = 2*y
    return x+y


def modify_list(lst, i, val):
    """ assign val to lst[i] does not return any value """
    if len(lst)>i:
        lst[i] = val
    return None

def increment(lst):
    for i in range(len(lst)):
        lst[i] = lst[i] + 1
    #no value returned (same as return None)
    

def nullify(lst):
    print(hex(id(lst)))
    lst = []
    print(hex(id(lst)))
    #no value returned (same as return None)


s = 0
def summation_local(n):
    s = sum(range(1,n+1))
    #no value returned (same as return None)


def summation_global(n):
    global s
    s = sum(range(1,n+1))
    #no value returned (same as return None)



def mydivmod(a,b):
    """ integer quotient and remainder of a divided by b """
    return a//b, a%b