Stepik task

a = [int(i) for i in input().split()]
y = 0
c = 1
b = []
for a[y] in a:
    if y == 0:
        sum1 = a[y + 1] + a[-y]
        b.insert(0, sum1)
    elif y == len(a):
        sum2 = a[y - 1] + a[0]
        b.insert(-1, sum2)
    else:
        while y < len(a):
            sum = a[y - 1] + a[y + 1]
            b.insert(c, sum)
            с += 1
            y += 1
print(b)