시간 제한메모리 제한제출정답맞힌 사람정답 비율
1 초 (추가 시간 없음) 256 MB111100.000%

문제

There is an array $a$ containing $n$ integers. Also, there is initially empty array $b$. Some elements of $a$ are going to be added to $b$. Each element is added with probability $P$ independently from others. Then the value of $s$ is to be computed: $$s = \oplus_{i = 0}^{|b|} b_{i}$$ where $\oplus$ is bitwise exclusive OR (if the array $b$ is empty, $s$ equals to zero). You are required to compute the expected value of $s^{2}$.

입력

The first line of input contains three integers $n$, $X$ and $Y$. The probability $P$ is equal to $\frac{X}{Y}$.

The second line contains $n$ integers $a_{i}$ divided by spaces --- elements of the array $a$.

출력

The answer can be always represented as a fraction $\frac{u}{v}$ where $u$ and $v$ are co-prime numbers and $v \neq 0 \mod (10^9+7)$ You are required to output only one number --- $u \times v^{-1} \mod (10^9+7)$

제한

  • $1 \le n \le 10^5$
  • $0 \le X < 10^9+7$
  • $0 < Y < 10^9+7$
  • $X \le Y$
  • $0 \le a_i < 10^9+7$

예제 입력 1

3 1 2
2 8 10

예제 출력 1

42