We will buy a product for N yen (the currency of Japan) at a shop.  If we use only 1000-yen bills to pay the price, how much change will we receive?  Assume we use the minimum number of bills required.
import math
a = int(input())
b = a
a = math.ceil(a/1000)
a = a * 1000
print(b-a)
import math
a = int(input())
b = a
a = math.ceil(a/1000)
a = a * 1000
print(a-b)