A rectangular display board has R rows and C columns of bulb sockets, each either holding a lit bulb or left empty. To minimize the amount of trim needed, the technician wants to build the smallest possible axis-aligned rectangular frame — with sides running along full rows and full columns of the board — that completely encloses every lit bulb. Given the state of every socket on the board, compute the area, in socket cells, of the smallest such frame. It is guaranteed that at least one bulb on the board is lit.

Input format

• Line 1: two space-separated integers R and C — the number of rows and columns of the board.
• Next R lines: each line is a string of exactly C characters, each either '0' (empty socket) or '1' (lit bulb), giving one row of the board from top to bottom.

Output format

• A single integer: the area of the smallest axis-aligned rectangle that contains every socket holding a lit bulb.

Constraints

• 1 <= R, C <= 1000
• Each of the R lines has length exactly C and consists only of '0' and '1'.
• At least one character across the whole board is '1'.

4 5
00000
01010
00100
00000

6

3 3
000
010
000

1