Note the unusual memory limit.

For a rectangular grid where each square is painted white or black, we define its complexity as follows:

• If all the squares are black or all the squares are white, the complexity is 0.
• Otherwise, divide the grid into two subgrids by a line parallel to one of the sides of the grid, and let c_1 and c_2 be the complexities of the subgrids. There can be multiple ways to perform the division, and let m be the minimum value of $\max(c_1, c_2)$ in those divisions. The complexity of the grid is m+1.

You are given a grid with H horizontal rows and W vertical columns where each square is painted white or black. HW characters from A_{11} to A_{HW} represent the colors of the squares. A_{ij} is # if the square at the i-th row from the top and the j-th column from the left is black, and A_{ij} is . if that square is white.

Find the complexity of the given grid.

Constraints

• $1 \leq H,W \leq 185$
• A_{ij} is # or ..

Input

Input is given from Standard Input in the following format:

H W
A_{11}A_{12}...A_{1W}
:
A_{H1}A_{H2}...A_{HW}

Output

Print the complexity of the given grid.

Examples

Input

3 3
...
.##
.##

Output

2

Input

6 7
.####.#
....#.
....#.
....#.
.####.#
....##

Output

4

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