时间限制：C/C++/Rust/Pascal 1秒，其他语言2秒
空间限制：C/C++/Rust/Pascal 256 M，其他语言512 M
64bit IO Format: %lld
空间限制：C/C++/Rust/Pascal 256 M，其他语言512 M
64bit IO Format: %lld
题目描述
Given a 
binary matrix. Please output the size of second large rectangle containing all 
.
Containing all means that the entries of the rectangle are all .
Containing all
A rectangle can be defined as four integers 
where 
and 
. Then, the rectangle is composed of all the cell (x, y) where 
and 
. If all of the cell in the rectangle is , this is a valid rectangle.
Please find out the size of the second largest rectangle, two rectangles are different if exists a cell belonged to one of them but not belonged to the other.
输入描述:
The first line of input contains two space-separated integers N and M.
Following N lines each contains M characters.
输出描述:
Output one line containing an integer representing the answer. If there are less than 2 rectangles containning all.