题目描述
Problem Description
Define a sequence:
$f(0) = a, f(1) = b, f(n) = f(n - 1) + f(n - 2)$
where $a, b$ are positive integers, and $n \geq 2$.
The question is how many pairs $(a, b)$ exist such that $k$ appears in this sequence and is not one of the first two terms.
Since the answer may be very large, you only need to output the result modulo $10^9 + 7$.
Input Format
A single line containing an integer $k$.
Output Format
A single line containing a number, representing the result modulo $10^9 + 7$.
Sample Input and Output
Sample Input #1
19260817
Sample Output #1
34166325
Sample Input #2
1000000000
Sample Output #2
773877569
Notes
$1 \leq k \leq 10^9$
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
19260817
样例输出
34166325