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.
def abc173_a():
    N = int(input())
    print(N%1000)
    
    
abc173_a()

def abc173_a():
    N = int(input())
    #N = 3000%1000
    if N%1000 ==  0:
        print(0)
    else:
        print(1000-N%1000)






abc173_a()
