A, B, C = map(int, input().split())
flag = 0
for i in range(100):
	if A * i - B > 0 and A * i - B == C:
		print(i)
		flag = 1
	elif A * i > 0 and A * i == C:
		print(i)
		flag = 1
if flag == 0:
	print(-1)