Network
In your company's computer network, there are n computers. Due to a malfunctioning switch, not all pairs of computers can communicate with each other. Additionally, if computer a is exchanging information with computer b, no other computers can communicate with either a or b during that time. Your task is to determine the maximum number of computers that can simultaneously engage in exchanging information.
Input
The first line of the input contains the integer n (1 ≤ n ≤ 18). This is followed by n lines, each containing n characters. The j-th character of the i-th line is "Y" if computers i and j can exchange information, and "N" otherwise. Note that the i-th character of the i-th line is always "N", and the character matrix is symmetric.
Output
Print the maximum number of computers that can simultaneously participate in exchanging information.