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A8978 | Perfect Pair

时间限制1s
内存限制256MB
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题目描述

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?

输入格式

Single line of the input contains three integers $x$ , $y$ and $m$ ( $-10^{18}<=x$ , $y$ , $m<=10^{18}$ ).

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.

输出格式

Print the minimum number of operations or "-1" (without quotes), if it is impossible to transform the given pair to the $m$ -perfect one.

输入输出样例

输入 #1
1 2 5
输出 #1
2
输入 #2
-1 4 15
输出 #2
4
输入 #3
0 -1 5
输出 #3
-1
C++ 编辑器
输入
输出