The farmer decided to build a barn on his farm. But on his farm there are trees and other buildings, which he does not want to remove.
For simplicity, we represent the farm as a rectangular grid of height and width . Each of the trees and buildings are located in one or more cells of the grid. The barn is a rectangle and should be built on the free cells of the grid.
Help the farmer to find out how many ways there are to place the barn, for all possible sizes of barns.
The first line contains two integers and - the dimensions of the farm.
The next lines contains description of the farm: each line contains characters - 0 or 1 (1 means the cell is available/free for building the barn).
Write lines with integers in each line. The value in the line must be equal to the number of ways to place a barn with height and width in the farm.