Problem E

Statement
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Description:
Let's define a function $$$f(p)$$$ on a permutation $$$p$$$ as follows. Let $$$g_i$$$ be the greatest common divisor (GCD) of elements $$$p_1$$$, $$$p_2$$$, ..., $$$p_i$$$ (in other words, it is the GCD of the prefix of length $$$i$$$). Then $$$f(p)$$$ is the number of distinct elements among $$$g_1$$$, $$$g_2$$$, ..., $$$g_n$$$.

Let $$$f_{max}(n)$$$ be the maximum value of $$$f(p)$$$ among all permutations $$$p$$$ of integers $$$1$$$, $$$2$$$, ..., $$$n$$$.

Given an integers $$$n$$$, count the number of permutations $$$p$$$ of integers $$$1$$$, $$$2$$$, ..., $$$n$$$, such that $$$f(p)$$$ is equal to $$$f_{max}(n)$$$. Since the answer may be large, print the remainder of its division by $$$1000\,000\,007 = 10^9 + 7$$$.

Input Format:
The only line contains the integer $$$n$$$ ($$$2 \le n \le 10^6$$$) — the length of the permutations.

Output Format:
The only line should contain your answer modulo $$$10^9+7$$$.

Note:
Consider the second example: these are the permutations of length $$$3$$$:

- $$$[1,2,3]$$$, $$$f(p)=1$$$.
- $$$[1,3,2]$$$, $$$f(p)=1$$$.
- $$$[2,1,3]$$$, $$$f(p)=2$$$.
- $$$[2,3,1]$$$, $$$f(p)=2$$$.
- $$$[3,1,2]$$$, $$$f(p)=2$$$.
- $$$[3,2,1]$$$, $$$f(p)=2$$$.

The maximum value $$$f_{max}(3) = 2$$$, and there are $$$4$$$ permutations $$$p$$$ such that $$$f(p)=2$$$.

Submissions

IDLanguageExit CodeTimestampCodeStdoutStderrRetry
4835 go 0 2026-03-04T06:16:44.163357Z View View View Retry

Evaluations

Eval IDRun IDProviderModelLangSuccessTimestampPromptResponseStdoutStderrRetry
3224 20260320-230005 gemini gemini-3-pro-preview go true 2026-03-20T23:43:57.198238Z View View View View Retry
1478 20260302-072902 openai gpt-5 go false 2026-03-02T10:02:26.503367Z View View View View Retry
1474 20260302-072902 openai gpt-5 go true 2026-03-02T09:42:00.612178Z View View View View Retry