codeforces#P1749D. Counting Arrays

Counting Arrays

Description

Consider an array $a$ of length $n$ with elements numbered from $1$ to $n$. It is possible to remove the $i$-th element of $a$ if $gcd(a_i, i) = 1$, where $gcd$ denotes the greatest common divisor. After an element is removed, the elements to the right are shifted to the left by one position.

An array $b$ with $n$ integers such that $1 \le b_i \le n - i + 1$ is a removal sequence for the array $a$ if it is possible to remove all elements of $a$, if you remove the $b_1$-th element, then the $b_2$-th, ..., then the $b_n$-th element. For example, let $a = [42, 314]$:

  • $[1, 1]$ is a removal sequence: when you remove the $1$-st element of the array, the condition $gcd(42, 1) = 1$ holds, and the array becomes $[314]$; when you remove the $1$-st element again, the condition $gcd(314, 1) = 1$ holds, and the array becomes empty.
  • $[2, 1]$ is not a removal sequence: when you try to remove the $2$-nd element, the condition $gcd(314, 2) = 1$ is false.

An array is ambiguous if it has at least two removal sequences. For example, the array $[1, 2, 5]$ is ambiguous: it has removal sequences $[3, 1, 1]$ and $[1, 2, 1]$. The array $[42, 314]$ is not ambiguous: the only removal sequence it has is $[1, 1]$.

You are given two integers $n$ and $m$. You have to calculate the number of ambiguous arrays $a$ such that the length of $a$ is from $1$ to $n$ and each $a_i$ is an integer from $1$ to $m$.

The only line of the input contains two integers $n$ and $m$ ($2 \le n \le 3 \cdot 10^5$; $1 \le m \le 10^{12}$).

Print one integer — the number of ambiguous arrays $a$ such that the length of $a$ is from $1$ to $n$ and each $a_i$ is an integer from $1$ to $m$. Since the answer can be very large, print it modulo $998244353$.

Input

The only line of the input contains two integers $n$ and $m$ ($2 \le n \le 3 \cdot 10^5$; $1 \le m \le 10^{12}$).

Output

Print one integer — the number of ambiguous arrays $a$ such that the length of $a$ is from $1$ to $n$ and each $a_i$ is an integer from $1$ to $m$. Since the answer can be very large, print it modulo $998244353$.

2 3
4 2
4 6
1337 424242424242
6
26
1494
119112628