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("N:"))
sa = 10000 - N
ans = sa % 1000
print(ans)
N = int(input())

sa = 10000 - N
ans = sa % 1000

print(ans)