Color Circle

Time Limit: 1s

Memory Limit: 65535k

Description

There are colorful flowers in the parterre in front of the door of college and form many beautiful patterns. Now, you want to find a circle consist of flowers with same color. What should be done ? Assuming the flowers arranged as matrix in parterre, indicated by a N*M matrix. Every point in the matrix indicates the color of a flower. We use the same uppercase letter to represent the same kind of color. We think a sequence of points d1, d2, … dk makes up a circle while: 1. Every point is different. 2. k >= 4 3. All points belong to the same color. 4. For 1 <= i <= k-1, di is adjacent to di+1 and dk is adjacent to d1. ( Point x is adjacent to Point y while they have the common edge). N, M <= 50. Judge if there is a circle in the given matrix.

Input

There are multiply test cases. In each case, the first line are two integers n and m, the 2^(nd) ~ n+1th lines is the given n*m matrix. Input m characters in per line.

Output

Output your answer as “Yes” or ”No” in one line for each case

Sample Input

3 3
AAA
ABA
AAA

Sample Output

Yes

Hint

None

Source

None

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