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5523: Appleman and Complicated Task

内存限制：256 MB 时间限制：2 S
题面：传统 评测方式：文本比较 上传者：
提交：1 通过：1
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题目描述

D. Appleman and Complicated Task
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
Toastman came up with a very complicated task. He gives it to Appleman, but Appleman doesn't know how to solve it. Can you help him?
Given a n×n checkerboard. Each cell of the board has either character 'x', or character 'o', or nothing. How many ways to fill all the empty cells with 'x' or 'o' (each cell must contain only one character in the end) are there, such that for each cell the number of adjacent cells with 'o' will be even? Find the number of ways modulo 1000000007 (109+7). Two cells of the board are adjacent if they share a side.
Input
The first line contains two integers n, k (1≤n,k≤105) − the size of the board, and the number of cells that has characters initially.
Then k lines follows. The i-th line contains two integers and a character: ai, bi, ci (1≤ai,bi≤n; ci is either 'o' or 'x'). This line means: there is a character ci in the cell that is located on the intersection of the ai-th row and bi-th column. All the given cells are distinct.
Consider that the rows are numbered from 1 to n from top to bottom. Analogically, the columns are numbered from 1 to n from left to right.
Output
Print a single integer − the answer to the problem.
Examples
Input 
3 2
1 1 x
2 2 o
Output 
2
Input 
4 3
2 4 x
3 4 x
3 2 x
Output 
2
Note
In the first example there are two ways: 
 xxo          xoo
 xox          ooo
 oxx          oox

输入样例 复制

输出样例 复制

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