#
# A program that shows that list members value might be changed 
# in a function

def main():
    x=[10,-10,20,30,-21]

    print("The initial list x: \t \t ",x)

    modify(x)

    print("The list x after modify(x) call:",x)

def modify(a):
    for i in range(5):
        print("Adding 20 to",a[i],"...")
        a[i]=a[i]+20

main()