You went shopping to buy cakes and donuts with X yen (the currency of Japan).  First, you bought one cake for A yen at a cake shop. Then, you bought as many donuts as possible for B yen each, at a donut shop.  How much do you have left after shopping?
X = int(input())
A = int(input())
B = int(input())

print(X - A % B)

X = int(input())
A = int(input())
B = int(input())

print((X - A) % B)
