P9290 [AtCoder] AtCoder Grand Contest 013 - Piling Up
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题目描述

Joisino has a lot of red and blue bricks and a large box. She will build a tower of these bricks in the following manner.

First, she will pick a total of N bricks and put them into the box. Here, there may be any number of bricks of each color in the box, as long as there are N bricks in total. Particularly, there may be zero red bricks or zero blue bricks. Then, she will repeat an operation M times, which consists of the following three steps:

  • Take out an arbitrary brick from the box.
  • Put one red brick and one blue brick into the box.
  • Take out another arbitrary brick from the box.

After the M operations, Joisino will build a tower by stacking the $2 \times M$ bricks removed from the box, in the order they are taken out. She is interested in the following question: how many different sequences of colors of these $2 \times M$ bricks are possible? Write a program to find the answer. Since it can be extremely large, print the count modulo 10^9+7.

Constraints

  • $1 \leq N \leq 3000$
  • $1 \leq M \leq 3000$

Input

Input is given from Standard Input in the following format:

N M

Output

Print the count of the different possible sequences of colors of $2 \times M$ bricks that will be stacked, modulo 10^9+7.

Examples

Input

2 3

Output

56

Input

1000 10

Output

1048576

Input

1000 3000

Output

693347555

输入格式

见题面

输出格式

见题面

样例输入
1000 3000
样例输出
693347555