Let us call a pair of integer numbers *m*-perfect, if at least one number in the pair is greater than or equal to *m*. Thus, the pairs (3, 3) and (0, 2) are 2-perfect while the pair (-1, 1) is not.

Two integers *x*, *y* are written on the blackboard. It is allowed to erase one of them and replace it with the sum of the numbers, (*x* + *y*).

What is the minimum number of such operations one has to perform in order to make the given pair of integers *m*-perfect?
Single line of the input contains three integers *x*, *y* and *m* ( - 10<sup class="upper-index">18</sup> ≤ *x*, *y*, *m* ≤ 10<sup class="upper-index">18</sup>).

Please, do not use the %lld specifier to read or write 64-bit integers in C++. It is preffered to use the cin, cout streams or the %I64d specifier.
A, B, C = map(int, input().split())

ans = 0

if A > B:
	temp = A
	A = B
	B = temp
if B >= C:
	print(0)
	exit(0)
if A <= 0 and B <= 0:
	print(-1)
	exit(0)
if A < 0:
	ans = (-A) // B
	A = A + ans * B
for i in range(1, 1000000000):
	if A + B >= C:
		print(ans + i);
		exit(0)
	temp = A + B
	A = B
	B = temp

