Problem Statement
You are given an integer sequence of length $N$: $A_1,A_2,...,A_N$. Let us perform $Q$ operations in order. The $i$-th operation is described by two integers $X_i$ and $Y_i$. In this operation, we will choose one of the following two actions and perform it:
- Swap the values of
$A_{X_i}$and$A_{Y_i}$ - Do nothing
There are $2^Q$ ways to perform these operations. Find the sum of the inversion numbers of the final sequences for all of these ways to perform operations, modulo $10^9+7$.
Here, the inversion number of a sequence $P_1,P_2,...,P_M$ is the number of pairs of integers $(i,j)$ such that $1\leq i < j\leq M$ and $P_i > P_j$.
Constraints
$1 \leq N \leq 3000$$0 \leq Q \leq 3000$$0 \leq A_i \leq 10^9(1\leq i\leq N)$$1 \leq X_i,Y_i \leq N(1\leq i\leq Q)$$X_i\neq Y_i(1\leq i\leq Q)$- All values in input are integers.
Input
Input is given from Standard Input in the following format:
N Q
A_1
:
A_N
X_1 Y_1
:
X_Q Y_Q
Output
Print the sum of the inversion numbers of the final sequences, modulo $10^9+7$.
样例
3 2
1
2
3
1 2
1 3
6
5 3
3
2
3
1
4
1 5
2 3
4 2
36
9 5
3
1
4
1
5
9
2
6
5
3 5
8 9
7 9
3 2
3 8
425
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