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 = input()
print(n[-3:])
n = int(input())
x = n % 1000

if x == 0 :
    print(0)
else :
    print(1000 - x)