2335: Color Circle

     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. 

     There are multiply test cases.

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

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

3 3
AAA
ABA
AAA

Yes