Harps and Tails

Gary likes the Celtic harp on the 1 euro coin. He has a grid of such coins with $n$ rows and $m$ columns. Each coin lies with either the harp or the tail facing up.

Gary wants as many rows as possible to show a harp in every cell. He is allowed one operation: choose a column and turn over every coin in that column. A coin that showed the harp then shows the tail, and a coin that showed the tail then shows the harp.

Gary may repeat the operation as many times as he likes. Find the largest number of rows that show a harp in every cell once he stops.

The first line contains the number of rows $n$ and the number of columns $m$, separated by a space ($1 \le n, m \le 1000$).

Each of the next $n$ lines contains a string of length $m$ describing one row of the grid. The $j$-th character of the $i$-th line is 'T' if the coin in row $i$, column $j$ shows a tail, and 'H' if it shows the harp.

Print one line with the largest possible number of rows that show a harp in every cell.