Hi friends This question was asked in recent hiring challenge at hackerearth , that is over now,Please discuss your strategies.I am not able to devise algorithm please provide some hints to solve it.

Pulkit is really good at maths. Recently, he came to know about a problem on matrices. Amazed by the problem he got, he asked Ashish the same problem. Ashish also being good at maths solved the problem within 5 minutes. Now, its your time to solve the problem.

You will be given n*m binary matrix. You need to tell if it is possible to delete a column such that after deleting that column, rows of the matrix will be unique. If yes than print “Yes” else print “No”.

[Input]

First line contains an integer t denoting no.of test cases.

Next line contains 2 integers n and m denoting no.of rows and columns.

Next n line contains binary string of length m each.

[Output]

For each test case output “Yes” or “No”.

[Constraints]

1<=t<=100

1<=n<=1000

2<=m<=1000

Sample Input (Plaintext Link)

2

3 3

101

000

100

2 2

11

11

Sample Output (Plaintext Link)

Yes

No