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())
for i in range(1, 10+1):
    if (i*1000) - N > 0:
        print((i-1)*1000 - N)
        break


N = int(input())
for i in range(1, 10+1):
    if (i*1000) - N >= 0:
        print((i)*1000 - N)
        break

