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.
def main():
  n = int(input())
  print(n % 1000)
  
main()
import math

def main():
  n = int(input())
  t = (int(math.ceil(n / 1000))) * 1000
  print(t - n)

main()