Problem1027--「一本通 1.4 例 1」电路维修

### 1027: 「一本通 1.4 例 1」电路维修

Time Limit: 0 Sec  Memory Limit: 128 MB
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#### Description

N×MN\times M 个这样的元件，你想将其排列成 NNMM 列放在电路板上。电路板的左上角连接电源，右下角连接灯泡。

Casper is designing an electronic circuit on a N×MN ×M rectangular grid plate. There are N×MN ×M square tiles that are aligned to the grid on the plate. Two (out of four) opposite corners of each tile are connected by a wire.
A power source is connected to the top left corner of the plate. A lamp is connected to the bottom right corner of the plate. The lamp is on only if there is a path of wires connecting power source to lamp. In order to switch the lamp on, any number of tiles can be turned by 90°90° (in both directions).
In the picture above the lamp is off. If any one of the tiles in the second column from the right is turned by 90°90° , power source and lamp get connected, and the lamp is on.
Write a program to find out the minimal number of tiles that have to be turned by 90°90° to switch the lamp on.

#### Input

The first line of input contains two integer numbers NN and MM, the dimensions of the plate. In each of the following NN lines there are MM symbols – either \texttt{\\} or /\texttt{/} – which indicate the direction of the wire connecting the opposite vertices of the corresponding tile.

#### Output

There must be exactly one line of output. If it is possible to switch the lamp on, this line must contain only one integer number: the minimal number of tiles that have to be turned to switch on the lamp. If it is not possible, output the string: NO SOLUTION\texttt{NO SOLUTION}

#### Sample Input

3 5
\\/\\
\\///
/\\\\

#### Sample Output

1