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.
N = int(input())

ans = 0

while N > 1000:
  N = N - 1000

print(ans)
N = int(input())

ans = 0

while N >= 1000:
  N = N - 1000

if N == 0:
  print(0)
else:
  ans = 1000 - N
  print(ans)