def linear_search(alist, key):

"""Return index of key in alist. Return -1 if key not present."""

for i in range(len(alist)):

if alist[i] == key:

return i

return -1

alist = input('Enter the list of numbers: ')

alist = alist.split()

alist = [int(x) for x in alist]

key = int(input('The number to search for: '))

index = linear_search(alist, key)

if index < 0:

print('{} was not found.'.format(key))

else:

print('{} was found at index {}.'.format(key, index))