summing digits of a number

[Megabeaz]

I've a problem with my code
get a number from user then summing digits of that number

num = input()
y = 0
for x in range(0, len(num)):

    y = int(num[x:x+1]) + int(num[x+1:x+2]) + y

print(y)

i cant finger out what's the problem
(my native language isn't English so may i have some mistakes)