题目描述
Problem Statement
Consider sequences {A_1,...,A_N} of length N consisting of integers between 1 and K (inclusive).
There are K^N such sequences. Find the sum of $\gcd(A_1, ..., A_N)$ over all of them.
Since this sum can be enormous, print the value modulo (10^9+7).
Here $\gcd(A_1, ..., A_N)$ denotes the greatest common divisor of A_1, ..., A_N.
Input
Input is given from Standard Input in the following format:
N K
Output
Print the sum of $\gcd(A_1, ..., A_N)$ over all K^N sequences, modulo (10^9+7).
Constraints
- $2 \leq N \leq 10^5$
- $1 \leq K \leq 10^5$
- All values in input are integers.
Sample Input 1
3 2
Sample Output 1
9
$\gcd(1,1,1)+\gcd(1,1,2)+\gcd(1,2,1)+\gcd(1,2,2)$
$+\gcd(2,1,1)+\gcd(2,1,2)+\gcd(2,2,1)+\gcd(2,2,2)$
=1+1+1+1+1+1+1+2=9
Thus, the answer is 9.
Sample Input 2
3 200
Sample Output 2
10813692
Sample Input 3
100000 100000
Sample Output 3
742202979
Be sure to print the sum modulo (10^9+7).
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分