题目描述Description

One day DOGGOD_Q and his friend went to a university for CCSP, they suddenly saw a huge board，which was printed with various school badges, so DOGGOD_Q talked with his friend:

DOGGOD_Q: Let's find out where our badge is!

friend: It's over there, blue and white.

DOGGOD_Q understood, it turns out that as long as the school badge has and only blue and white, this is our school badge. Now we turn some of the badges into a phalanx of n*m, and use an uppercase letter to indicate the color of this position (B is Blue, W is White, different color must have different uppercase letter), When this school badge has only blue and white colors, we can say it is our school badge, please write a program to judge it.

输入格式Input

The first line contains one integer T (1 \leq T \leq 100) which is the number of test cases.

The first line of the test case contains two integers n and m (1 \leq n, m \leq 100) which mean the size of phalanx.

Next follow n line each line has m uppercase letter, which indicate the color of this position.

输出格式Output

For each test case, print the answer – if it is our school badge, print “Yes”, otherwise print “No”.

样例Sample

出题Author

DOGGOD_Q

来源Source