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 sys

def main():

	N = int(input())
	print(N%1000)

if __name__ == "__main__":
    main()
import sys

def main():

	N = int(input())
	m = N%1000
	if m == 0 :
		print(0)
	else:
		print(1000 - m)

if __name__ == "__main__":
    main()